As filed with the Securities and Exchange Commission on September 11, 2013

Securities Act File No. 033-37537

Investment Company Act File No. 811-06211

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933	x
Pre-Effective Amendment No.	¨
Post-Effective Amendment No. 31	x
and/or
REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940	x
Amendment No. 32	x
(Check appropriate box or boxes)

Ready Assets U.S. Treasury Money Fund

(Exact Name of Registrant as Specified in Charter)

100 Bellevue Parkway

Wilmington, Delaware 19809

(Address of Principal Executive Office)

Registrant’s Telephone Number, including Area Code (800) 441-7762

John M. Perlowski

Ready Assets U.S. Treasury Money Fund

55 East 52^nd Street

New York, New York 10055

United States of America

(Name and Address of Agent for Service)

Copies to:

Frank P. Bruno, Esq.	Benjamin Archibald, Esq.
Sidley Austin LLP	BlackRock Advisors, LLC
787 Seventh Avenue	55 East 52nd Street
New York, New York 10019-6018	New York, New York 10055

It is proposed that this filing will become effective (check appropriate box)

x Immediately upon filing pursuant to paragraph (b)

¨ On (date) pursuant to paragraph (b)

¨ 60 days after filing pursuant to paragraph (a)(1)

¨ On (date) pursuant to paragraph (a)(1)

¨ 75 days after filing pursuant to paragraph (a)(2)

¨ On (date) pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

¨ This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

Title of Securities Being Registered: Shares of beneficial interest, par value $.10 per share.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all of the requirements for the effectiveness of this Post-Effective Amendment to the Registration Statement pursuant to Rule 485(b) under the Securities Act and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of New York and the State of New York, on September 11, 2013.

READY ASSETS U.S. TREASURY MONEY FUND
	(Registrant)
By	/s/    JOHN M. PERLOWSKI
	John M. Perlowski President and Chief Executive Officer

Pursuant to the requirements of the Securities Act of 1933, this Post-Effective Amendment to its Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.

Signature	Title	Date
/s/    JOHN M. PERLOWSKI John M. Perlowski	President and Chief Executive Officer (Principal Executive Officer)	September 11, 2013
/s/    NEAL J. ANDREWS Neal J. Andrews	Chief Financial Officer (Principal Financial and Accounting Officer)	September 11, 2013
DAVID O. BEIM* David O. Beim	Trustee
RONALD W. FORBES* Ronald W. Forbes	Trustee
DR. MATINA S. HORNER* Dr. Matina S. Horner	Trustee
RODNEY D. JOHNSON* Rodney D. Johnson	Trustee
HERBERT I. LONDON* Herbert I. London	Trustee
IAN A. MACKINNON* Ian A. MacKinnon	Trustee
CYNTHIA A. MONTGOMERY* Cynthia A. Montgomery	Trustee
JOSEPH P. PLATT* Joseph P. Platt	Trustee
ROBERT C. ROBB, JR.* Robert C. Robb, Jr.	Trustee
TOBY ROSENBLATT* Toby Rosenblatt	Trustee
KENNETH L. URISH* Kenneth L. Urish	Trustee

2

FREDERICK W. WINTER* Frederick W. Winter	Trustee
PAUL L. AUDET* Paul L. Audet	Trustee
HENRY GABBAY* Henry Gabbay	Trustee

*By: /s/    BENJAMIN ARCHIBALD Benjamin Archibald (Attorney-in-Fact) September 11, 2013

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EXHIBIT INDEX

Index No.	Description of Exhibit
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase