UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 8-K

CURRENT REPORT
Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported) January 12, 2004

Merrill Lynch Mortgage Investors, Inc. (as depositor under the Pooling and Servicing Agreement, dated as of November 1, 2003, relating to the Merrill Lynch Mortgage Trust 2003-KEY1, Commercial Mortgage Pass-Through Certificates, Series 2003-KEY1)
(Exact name of registrant as specified in its charter)

Delaware
(State or other jurisdiction
of incorporation)

333-108378
(Commission
File Number)

13-3416059
(IRS Employer
Identification No.)

4 World Financial Center, 10th Floor, 250 Vesey Street, NY, NY
(Address of principal executive offices)

10080
(Zip Code)

Registrant's telephone number, including area code 212-449-1000

(Former name or former address, if changed since last report.)

Item 5. Other Events and Regulation FD Disclosure.

This current report on Form 8-K relates to the monthly distribution reported to the holders of Merrill Lynch Mortgage Trust 2003-KEY1, Commercial Mortgage Pass-Through Certificates Series 2003-KEY1, which was made on January 12, 2004.

Item 7. Financial Statements and Exhibits.

99.1 Monthly Distribution Report, Pursuant to Section 4.02 of the Pooling and Servicing Agreement. for the distribution on January 12, 2004.
(Exhibit No. Description)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

LASALLE BANK NATIONAL ASSOCIATION, IN ITS CAPACITY AS TRUSTEE UNDER THE POOLING AND SERVICING AGREEMENT ON BEHALF OF MERRILL LYNCH MORTGAGE INVESTORS, INC., REGISTRANT

Date: January 12, 2004

By: /s/ Russell Goldenberg
Russell Goldenberg
Group Senior Vice President

MERRILL LYNCH COMM MORT PS THR CERTS SER 2003-KEY1 8-K