Pioneer Series Trust X

Filed: 27 Jun 12, 8:00pm
					            Exhibit A

Pioneer Series Trust X
60 State Street
Boston, Massachusetts 02110

June 28, 2012

Securities and Exchange Commission
Division of Investment Management
100 F Street, NE
Washington, D.C. 20549

Re:	Pioneer Series Trust X
	Registration Statement on Form N-1A
	(File Nos. 333-89354; 811-21108)

Ladies and Gentlemen:

In connection with the review by the Staff of the Securities and Exchange
Commission (the "Commission") of Post-Effective Amendment No. 17 to the
Registration Statement on Form N-1A of Pioneer Series Trust X (the
"Registrant"), filed on April 9, 2012 with respect to its series Pioneer
Multi-Asset Ultrashort Income Fund (formerly, Pioneer Multi-Asset Floating
Rate Fund), the Registrant acknowledges that, with respect to filings
made by the Registrant with the Commission and reviewed by the Staff:

(a)   the Registrant is responsible for the adequacy and accuracy of
the disclosure in the filings;

(b)   Staff comments or changes to disclosure in response to Staff
comments in the filings reviewed by the Staff do not foreclose the
Commission from taking any action with respect to the filings; and

(c)	the Registrant may not assert Staff comments as a defense in any
proceeding initiated by the Commission or any person under the federal
securities laws of the United States.


Pioneer Series Trust X

By:   /s/Christopher Kelley
Name:    Christopher J. Kelley
Title:   Secretary