Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, or a non-accelerated filer. See definition of “accelerated filer and large accelerated filer” in Rule 12b-2 of the Exchange Act. (Check one):

      Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act Rule 12b-2)Act).     Yes o          No þ

      As of October 31, 2005,April 30, 2006, there were 79,671,531 shares of the Common Stock of the registrant outstanding. The number of outstanding shares of Common Stock may not be meaningful, because as part of athe registrant’s plan of reorganization for the registrant, it is likely that the equity interests of the Company’s existing stockholders willare expected to be cancelled without consideration.

     Background. Kaiser Aluminum Corporation (“Kaiser”, “KAC” or the “Company”), its wholly owned subsidiary, Kaiser Aluminum & Chemical Corporation (“KACC”), and 24 of KACC’s subsidiaries have filed separate voluntary petitions in the United States Bankruptcy Court for the District of Delaware (the “Court”) for reorganization under Chapter 11 of the United States Bankruptcy Code (the “Code”); the Company, KACC and 15 of KACC’s subsidiaries (the “Original Debtors”) filed in the first quarter of 2002 and nine additional KACC subsidiaries (the “Additional Debtors”) filed in the first quarter of 2003. In December 2005, four of the KACC subsidiaries were dissolved pursuant to two separate plans of liquidation as more fully discussed below. The Company, KACC and the remaining 20 KACC subsidiaries continue to manage their businesses in the ordinary course asdebtors-in-possession subject to the control and administration of the Court. The Original Debtors and Additional Debtors are collectively referred to herein as the “Debtors” and the Chapter 11 proceedings of these entities are collectively referred to herein as the “Cases.“Cases” and the Company, KACC and the remaining 20 KACC subsidiaries are collectively referred to herein as the “Reorganizing Debtors.” For purposes of this Report, the term “Filing Date” means, with respect to any particular Debtor, the date on which such Debtor filed its Case. None of KACC’snon-U.S. joint ventures were included in the Cases. The Cases are being jointly administered. The Debtors are managing their businesses in the ordinary course as debtors-in-possession subject to the control and administration of the Court.

      During the first quarter of 2002, the Original Debtors filed separate voluntary petitions for reorganization. The wholly owned subsidiaries of KACC included in such filings were: Kaiser Bellwood Corporation (“Bellwood”), Kaiser Aluminium International, Inc. (“KAII”), Kaiser Aluminum Technical Services, Inc. (“KATSI”), Kaiser Alumina Australia Corporation (“KAAC”) (and its wholly owned subsidiary, Kaiser Finance Corporation (“KFC”)) and ten other entities with limited balances or activities.

      The Original Debtors found it necessary to file the Cases primarily because of liquidity and cash flow problems of the Company and its subsidiaries that arose in late 2001 and early 2002. The Company was facing significant near-term debt maturities at a time of unusually weak aluminum industry business conditions, depressed aluminum prices and a broad economic slowdown that was further exacerbated by the events of September 11, 2001. In addition, the Company had become increasingly burdened by asbestos litigation and growing legacy obligations for retiree medical and pension costs. The confluence of these factors created the prospect of continuing operating losses and negative cash flows, resulting in lower credit ratings and an inability to access the capital markets.

      On January 14, 2003, the Additional Debtors filed separate voluntary petitions for reorganization. The wholly owned subsidiaries included in such filings were: Kaiser Bauxite Company (“KBC”), Kaiser Jamaica Corporation (“KJC”), Alpart Jamaica Inc. (“AJI”), Kaiser Aluminum & Chemical of Canada Limited (“KACOCL”) and five other entities with limited balances or activities. Ancillary proceedings in respect of KACOCL and two other Additional Debtors were also commenced in Canada simultaneously with the January 14, 2003 filings.

      The Cases filed by the Additional Debtors were commenced, among other reasons, to protect the assets held by these Debtors against possible statutory liens that might have arisen and been enforced by the Pension Benefit Guaranty Corporation (“PBGC”) primarily as a result of the Company’s failure to meet a $17.0 accelerated funding requirement to its salaried employee retirement plan in January 2003 (see Note 810 for additional information regarding the accelerated funding requirement). The filing of the Cases by the Additional Debtors had no impact on the Company’s day-to-dayday-to-day operations.

      The outstanding principal of, and accrued interest on, all debt of the Debtors became immediately due and payable upon commencement of the Cases. However, the vast majority of the claims in existence at the

     Case Administration. Generally, pre-Filing Date claims, including certain contingent or unliquidated claims, against the Debtors will fall into two categories: secured and unsecured. Under the Code, a creditor’s claim is treated as secured only to the extent of the value of the collateral securing such claim, with the balance of such claim being treated as unsecured. Unsecured and partially secured claims do not accrue interest after the Filing Date. A fully secured claim, however, does accrue interest after the Filing Date until the amount due and owing to the secured creditor, including interest accrued after the Filing Date, is equal to the value of the collateral securing such claim. The bar dates (established by the Court) by which holders of pre-Filing Date claims against the Debtors (other than asbestos-related personal injury claims) could file their claims have passed. Any holder of a claim that was required to file such claim by such bar date and did not do so may be barred from asserting such claim against any of the Debtors and, accordingly, may not be able to participate in any distribution in any of the Cases on account of such claim. The Company has not yet completed its analysis of all of the proofs of claim to determine their validity. However, during the course of the Cases, certain matters in respect of the claims have been resolved. Material provisions in respect of claim settlements are included in the accompanying financial statements and are fully disclosed elsewhere herein. The bar dates do not apply to asbestos-related personal injury claims, for which no bar date has been set.

      Two creditors’ committees, one representing the unsecured creditors (the “UCC”) and the other representing the asbestos claimants (the “ACC”), have been appointed as official committees in the Cases and, in accordance with the provisions of the Code, have the right to be heard on all matters that come before the Court. In August 2003, the Court approved the appointment of a committee of salaried retirees (the “1114 Committee” and, together with the UCC and the ACC, the “Committees”) with whom the Debtors have negotiated necessary changes, including the modification or termination, of certain retiree benefits (such as medical and insurance) under Section 1114 of the Code. The Committees, together with the Court-appointed legal representatives for (a) potential future asbestos claimants (the “Asbestos Futures’ Representative”) and (b) potential future silica and coal tar pitch volatile claimants (the “Silica/ CTPV Futures’ Representative” and, collectively with the Asbestos Futures” Representative, the “Futures’ Representatives”), have played and will continue to play important roles in the Cases and in the negotiation of the terms of any plan or plans of reorganization. The Debtors are required to bear certain costs and expenses for the Committees and the Futures’ Representatives, including those of their counsel and other advisors.

     Commodity-related and Inactive Subsidiaries.As provided bypreviously disclosed, the Code,Company generated net cash proceeds of approximately $686.8 from the Debtors had the exclusive rightsale of its interests in and related to propose a plan of reorganization for 120 days following the initial Filing Date. The Court has subsequently approved several extensions of the exclusivity period for all Debtors, the most recent of which is set to expire on January 31, 2006, and which also extended the exclusive period for solicitation of acceptance of such plan or plans through March 31, 2006. As more fully discussed below, KAC, KACC and the other Debtors that together include the Fabricated products operations and an interest in Anglesey AluminiumQueensland Alumina Limited (“Anglesey”QAL”), filed a plan and Alumina Partners of reorganizationJamaica (“Alpart”). The Company’s interests in and disclosure statement.related to QAL were owned by KAAC and KFC. The disclosure statement was approvedCompany’s interests in and related to Alpart were owned by AJI and KJC. Throughout 2005, the Court on September 8, 2005. The Company has begun the solicitation process for plan approval. Such process is expected to be completed by mid-November 2005. The Court has set November 16, 2005, as the date by which objectionsproceeds were being held in separate escrow accounts pending distribution to the plan must be filedcreditors of AJI, KJC, KAAC and January 9, 2006 and January 10, 2006 as dates for plan confirmation hearings. No assurances can be given thatKFC (collectively the Court will grant any further extensions of exclusivity that may be sought. If a plan of“Liquidating Subsidiaries”) pursuant to certain liquidating plans.

      As previously disclosed in accordance with the Liquidating Plans. The Liquidating Plans outline the specific treatment2004, a group of creditors and their estimated recoveries in respect of the Liquidating Subsidiaries under several possible scenarios. The Liquidating Plans state that, based on the various assumptions and estimates set forth therein, it was anticipated that: (1) the Liquidating Subsidiaries would have an aggregate of approximately $673.8 of cash available for distribution to creditors when the Liquidating Plans became effective; and (2) after payment of priority claims and trust expenses (initial reserves for both of which were estimated to be in the range of $37.0 to $46.0), and payments to KACC under the Intercompany Settlement Agreement (“Intercompany Agreement”holders (the “Sub Note Group”) (see discussion below), the Liquidating Subsidiaries would distribute available cash to the following claimholders in the following amounts:

      The Court ultimately approved the disclosure statements related to the Liquidating Plans in February 2005. In April 2005, voting results on the Liquidating Plans were filed with the Court by the Debtors’ claims agent. Based on these results, the Court determined that a sufficient volume of creditors (in number and amount) had voted to accept the Liquidating Plans to permit confirmation proceedings with respect to the Liquidating Plans to go forward even though the filing by the claims agent also indicated that holders of the Sub Notes, as a group, voted not to accept the Liquidating Plans. Accordingly, as discussed above, the Court has conducted a series of evidentiary hearings to determine the allocation of distributions among holders of the Senior Notes and the Sub Notes. In connection with those proceedings, to date, the Court hasalso determined that thethere could be an allocation to the Parish of St. James, State of Louisiana, Solid Waste Revenue Bonds would be(the “Revenue Bonds”) of up to $8.0 and has ruled against the position asserted by the separate group that holds both 9⁷/8% Senior Notes and the Sub Notes. The Court has not ruled in respect of the position asserted by the Sub Note Group. All briefing, evidentiary and other proceedings before

      On December 20, 2005, the Court have been completed and the parties await the Court’s ruling on these matters. All such rulings in respect of these matters will be subject to appeal. There can be no assurance as to whether or whenconfirmed the Liquidating Plans will be confirmed(subject to certain modifications). Pursuant to the Court’s order, the Liquidating Subsidiaries were authorized to make partial cash distributions to certain of their creditors, while reserving sufficient amounts for future distributions until the Court resolved the contractual subordination dispute among the creditors of these subsidiaries and for the payment of administrative and priority claims and trust expenses. The Court’s ruling did not resolve the dispute between the holders of the Senior Notes and the holders of the Sub Notes (more fully described below) regarding their respective entitlement to certain of the proceeds from sale of interests by the CourtLiquidating Subsidiaries (the “Senior Note-Sub Note Dispute”). However, as a result of the Court’s approval, all restricted cash or ultimately consummatedother assets held on behalf of or if confirmed and consummated, asby the Liquidating Subsidiaries were transferred to a trustee in accordance with the amount of distributions to be made to individual creditorsterms of the Liquidating Subsidiaries or KACC, or what impact anyPlans. The trustee was then authorized to make partial cash distributions after setting aside sufficient reserves for amounts subject to the Senior Note-Sub Note Dispute (approximately $213.0) and for the payment of administrative and priority claims and trust expenses (approximately $40.0). After such resolution may have onreserves, the Company and its ongoing reorganization efforts. Thepartial distribution totaled approximately $430.0, of which, pursuant to the Liquidating Plans, relate exclusivelyapproximately $196.0 was paid to AJI, KJC, KAACthe PBGC and KFC and will have no impact on$202.0 amount was paid to the normal, ongoing operationsindenture trustees for the Senior Notes for subsequent distribution to the holders of the Company’s Fabricated products business unit or other continuing operations.Senior Notes. Of the remaining partial distribution, approximately $21.0 was paid to KACC and $11.0 was paid to the PBGC on behalf of KACC. Partial distributions were made in late December 2005 and, in connection with the effectiveness of the Liquidating Plans, the Liquidating Subsidiaries were deemed to be dissolved and took the actions necessary to dissolve and terminate their corporate existence.

      Based on the objections and pleadings filed by the Sub Note Group and the group that holds Sub Notes and the Senior Notes and the assumptions and estimates upon which the Liquidating Plans are based, if the holders of Sub Notes were ultimately to prevail on their appeal, the Liquidating Plans indicated that it is possible that the holders of the Sub Notes could receive between approximately $67.0 and approximately $215.0 depending on whether the Sub Notes were determined to rank on par with a portion or all of the Senior Notes. Conversely, if the holders of the Senior Notes prevail on appeal, then the holders of the Sub Notes will receive no distributions under Liquidating Plans. The Company believes that the intent of the indentures in respect of the Senior Notes and the Sub Notes was to subordinate the claims of the Sub Note holders in respect of the subsidiary guarantors (including the Liquidating Subsidiaries) and that the Court’s ruling on December 22, 2005, was correct. The Company cannot predict, however, the ultimate resolution of the matters raised by the Sub Note Group, or the other group, on appeal, when any such resolution will occur, or what impact any such resolution may have on the Company, the Cases or distributions to affected note holders.

      The distributions in respect of the Liquidating Plans also settled substantially all amounts due between KACC and the creditors of the Liquidating Subsidiaries pursuant to the Intercompany Settlement Agreement (the “Intercompany Agreement”) that was approvedwent into affect in February 2005 other than certain payments of alternative minimum tax paid by the CourtCompany that it expects to recoup from the liquidating trust for the KAAC and KFC joint plan of liquidation (the “KAAC/ KFC Plan”) during the second half of 2006 in February 2005.connection with a 2005 tax return (see Note 9). The Intercompany Agreement also resolvesresolved substantially all other pre-andpre- and post-petition intercompany claims betweenamong the Debtors. The Intercompany Agreement provides, among other things, for payments of cash by AJI, KJC and KAAC from the sale of their respective interests in and related to Alumina Partners of Jamaica (“Alpart”) and QAL to KACC of at least $90.0 in respect of its intercompany claims against AJI, KJC and KAAC. Under the Intercompany Agreement, such payments would be increased or decreased for (1) net cash flows funded by or collected by KACC related to: (a) the Company’s interests in and related to Alpart from January 1, 2004 through July 1, 2004 (estimated to be approximately $21.0 collected by the Company); (b) the Company’s interests in and related to QAL from July 1, 2004 through KAAC’s emergence from Chapter 11 (estimated to be in the $20.0 range collected by the Company through September 30, 2005); and (c) third party costs and certain limited overhead of KACC’s activities related to the sale of AJI’s, KJC’s and KAAC’s respective interests in and related to Alpart and QAL and (2) any purchase price adjustments (other than incremental amounts related to alumina sales contracts to be transferred) pursuant to KACC’s sale of its interests in Alpart. As provided under the Intercompany Agreement, KACC was reimbursed for approximately $14.5 of payments made in the third quarter of 2004 to retire Alpart-related debt and $28.0 in November 2004 as a partial payment of Alpart-related sales proceeds. The Intercompany Agreement calls for the remaining payments to be made in specific increments to KACC upon the effective dates of the Liquidating Plans.

      ItKBC is anticipated that KBC will bebeing dealt with either separately or in concert with the KACC plan of reorganization as more fully discussed below.

     Entities Containing the Fabricated Products and Certain Other Operations. Under the Code, claims of individual creditors must generally be satisfied from the assets of the entity against which that creditor has a lawful claim. The claims against the entities containing the Fabricated products and certain other operations will have to be resolved from the available assets of KACC, KACOCL, and Bellwood, which generally include the fabricated products plants and their working capital, the interests in and related to Anglesey Aluminium Limited (“Anglesey”) and proceeds to be received by such entities from the Liquidating Subsidiaries under the Intercompany Agreement. Sixteen of the Reorganizing Debtors have no material ongoing activities or operations and have no material assets or liabilities other than intercompany claims (which were resolved pursuant to the Intercompany Agreement). The Company has previously disclosed that it believed that it is likely that most of these entities will ultimately be merged out of existence or dissolved in some manner.

      As previously disclosed, while the Company’s objective has been (and continues to be) to achieve the highest possible recoveries for all stakeholders, consistent with the Debtors’ abilities to pay, and to continue the operations of their core businesses, no assurances could be given as to the Company’s ability to achieve this objective. In fact, the Debtors have previously stated that their belief has been (and continues to be) that, in the aggregate, it was likely that their liabilities would be found to significantly exceed the fair value of their assets and that, therefore, the Debtors believed that, with limited exceptions, it was likely that substantially all pre-Filing Date claims would be settled at less than 100% of their face value and the equity interests of the Company’s stockholders would be cancelled without consideration.

      The Kaiser Aluminum Amended Plan, would, in general consistent with previously disclosed agreements and understandings reached with key creditor constituents, resolve(subject to the further conditions precedent as outlined below), resolves substantially all pre-Filing Date liabilities of the Remaining Debtors under a single joint plan of reorganization. In summary, the Kaiser Aluminum Amended Plan provides for the following principal elements:

      The Kaiser Aluminum Amended Plan was accepted by all classes of creditors entitled to vote on it and the Kaiser Aluminum Amended Plan was confirmed by the Court on February 6, 2006. The confirmation order remains subject to motions for review and appeals filed by certain of KACC’s insurers and must still be adopted or affirmed by the United States District Court. Other significant conditions to emergence include completion of the Company’s exit financing, listing of the new common stock on the NASDAQ stock market and formation of certain trusts for the benefit of different groups of tort claimants. As provided in the Kaiser Aluminum Amended Plan, once the Court’s confirmation order is adopted or affirmed by the United States District Court, even if the affirmation order is appealed, the Company can proceed to emerge if the United States District Court does not stay its order adopting or affirming the confirmation order and the key constituents in the Chapter 11 proceedings agree. Assuming the United States District Court adopts or affirms the confirmation order, the Company believes that it is possible that it will emerge during the second quarter of 2006 or early in the third quarter of 2006. No assuranceassurances can be given that the Kaiser Aluminum Amended PlanCourt’s confirmation order will ultimately receive the necessary approvalsbe adopted or affirmed by creditors, be confirmed by the Court, receive affirmation from the United States District Court or that the transactions contemplated by the Kaiser Aluminum Amended Plan will ultimately be consummated. The Company’s ability to ultimately emerge from the Cases is subject to a number of factors, including, among others, inherent market-related risks, Court approval for various matters and the confirmation of a plan of reorganization in accordance with the applicable bankruptcy law and, accordingly, no assurances can be given as to whether or when any plan or plans of reorganization will ultimately be confirmed. Further, the specific recoveries of individual creditors is dependent on, among other things, the total amount of claims against the Debtors as ultimately determined by the Court, the priority of the applicable claims, the amount of value available for distribution in respect of claims and the completion of the plan confirmation process consistent with applicable bankruptcy law. However, assuming there are no unexpected delays in the approval of the Kaiser Aluminum Amended Plan, it is possible that the Company could emerge from Chapter 11 during the first quarter of 2006.

      At emergence from Chapter 11, KACCthe Reorganizing Debtors will have to pay or otherwise provide for a material amount of claims. Such claims include accrued but unpaid professional fees, priority pension, tax and environmental claims, secured claims, and certain post-petition obligations (collectively, “Exit Costs”). KACCThe Company currently estimates that its Exit Costs will be in the range of $60.0$45.0 to $80.0. KACC$60.0. The Company currently expects to fund such Exit Costs using the proceeds to be received under the Intercompany Agreement together with existing cash resources and borrowing availability under an exit financing facility that would replace the current Post-Petition Credit Agreement (see Note 6)8). If payments made to the Company under the Intercompany Agreement together withfunding from existing cash resources and borrowing availability under an exit financing facility are not sufficient to pay or otherwise provide for all Exit Costs, the Company and KACC will not be able to emerge from Chapter 11 unless and until sufficient funding can be obtained. Management believes it will be able to successfully resolve any issues that may arise in respect of an exit financing facility or be able to negotiate a reasonable alternative. However, no assurance can be given in this regard.

      As discussed above, the Kaiser Aluminum Amended Plan contemplates that the VEBAs would receive 66.9% of the new common stock of the emerged entity. However, during May 2006, the Company was informed that the VEBAs have sold a portion of their interests in such new common stock (representing 8.1% of the emerging entity’s new common stock). As a result, the Company expects to contribute 58.8% of the new common stock to the VEBAs upon emergence. Additionally, during May 2006, the Company was informed that the PBGC intends to sell approximately $462.0 of its $616.0 allowed unsecured claim. As a result, the PBGC ownership in the emerged entity is currently expected to be approximately 4.6%.

Financial Statement Presentation. The accompanying consolidated financial statements have been prepared in accordance with American Institute of Certified Professional Accountants (“AICPA”) Statement of Position 90-7 (“SOP 90-7”),Financial Reporting by Entities in Reorganization Under the Bankruptcy Code, and on a going concern basis, which contemplates the realization of assets and the liquidation of liabilities in the ordinary course of business. However, as a result of the Cases, such realization of assets and liquidation of liabilities are subject to a significant number of uncertainties.

     Financial Information. Condensed consolidatingUnder SOP 90-7 disclosures are required to distinguish the balance sheet, income statement and cash flows amounts in the consolidated financial statements between Debtors and non-Debtors. The vast majority of financial information included in the consolidated financial statements relates to Debtors. Condensed combined financial information of the Debtors and non-Debtors arenon-Debtor subsidiaries included in the consolidated financial statements is set forth below:below.