MarketAxess (MKTX) 10-Q/A 2006 Q1 Quarterly report (amended)

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 10-Q/A

(Amendment No. 1)

þ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
EXCHANGE ACT OF 1934

For the quarterly period ended March 31, 2006

or

o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
EXCHANGE ACT OF 1934

For the transition period from                    to                    

Commission file number: 0-50670

MARKETAXESS HOLDINGS INC.

(Exact Name of Registrant as Specified in Its Charter)

DELAWARE	52-2230784
(State or Other Jurisdiction of	(IRS Employer Identification No.)
Incorporation or Organization)

140 Broadway, 42nd Floor
New York, New York	10005
(Address of Principal Executive Offices)	(Zip Code)

(212) 813-6000

(Registrant’s Telephone Number, Including Area Code)

Indicate by check mark whether the registrant:(1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.

Yesþ Noo

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):

Large accelerated filer o Accelerated Filer þ Non-accelerated filer o

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).

Yeso Noþ

At May 3, 2006, the number of shares of the registrant’s common stock outstanding was 30,593,808.

TABLE OF CONTENTS

PART II. OTHER INFORMATION
	Item 6. Exhibits
SIGNATURES
EXHIBIT INDEX
EX-31.1: CERTIFICATION
EX-31.2: CERTIFICATION

EXPLANATORY NOTE

     We are amending our Form 10-Q for the quarter ended March 31, 2006 to revise the officer certifications set forth in Exhibits 31.1 and 31.2 to reflect the language exactly as set forth in Item 601(b)(31) of Regulation S-K.

2

PART II. OTHER INFORMATION

Item 6.Exhibits

     Exhibit Listing

Number	Description
31.1	Certification by Chief Executive Officer pursuant to Exchange Act Rule 13a-14(a), as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
31.2	Certification by Chief Financial Officer pursuant to Exchange Act Rule 13a-14(a), as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002

3

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant has duly caused this Form 10-Q/A to be signed on its behalf by the undersigned, thereunto duly authorized.

	MARKETAXESS HOLDINGS INC.
Date: June 15, 2006	By:	/s/ RICHARD M. MCVEY
		Richard M. McVey
		President and Chief Executive Officer (principal executive officer)
Date: June 15, 2006	By:	/s/ JAMES N.B. RUCKER
		James N. B. Rucker
		Chief Financial Officer (principal financial and accounting officer)

EXHIBIT INDEX

EXHIBIT
31.1	Certification by Chief Executive Officer pursuant to Exchange Act Rule 13a-14(a), as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
31.2	Certification by Chief Financial Officer pursuant to Exchange Act Rule 13a-14(a), as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002