SECURITIES AND EXCHANGE COMMISSION

FORM 11-K

(Mark One)

For the fiscal year ended December 31, 2003

OR

For the transition period from            to

Commission File No. 0-2989

A. Full title of the plan and the address of the plan, if different from that of the issuer named below:

COMMERCE BANCSHARES PARTICIPATING INVESTMENT PLAN

B. Name of issuer of the securities held pursuant to the plan and the address of its principal executive office:

COMMERCE BANCSHARES, INC.

COMMERCE BANCSHARES PARTICIPATING INVESTMENT PLAN

TABLE OF CONTENTS

SIGNATURES

The Plan. Pursuant to the requirements of the Securities Exchange Act of 1934, the trustees (or other persons who administer the employee benefit plan) have duly caused this annual report to be signed on its behalf by the undersigned hereunto duly authorized.

Report of Independent Registered Public Accounting Firm

Plan Trustees and Participants
Commerce Bancshares Participating Investment Plan:

We have audited the accompanying statements of net assets available for benefits of the Commerce Bancshares Participating Investment Plan (the Plan) as of December 31, 2003 and 2002, and the related statements of changes in net assets available for benefits for each of the years in the three-year period ended December 31, 2003. These financial statements are the responsibility of the Plan’s management. Our responsibility is to express an opinion on these financial statements based on our audits.

We conducted our audits in accordance with the Standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

In our opinion, the financial statements referred to above present fairly, in all material respects, the net assets available for benefits of the Commerce Bancshares Participating Investment Plan at December 31, 2003 and 2002, and the changes in net assets available for benefits for each of the years in the three-year period ended December 31, 2003, in conformity with U.S. generally accepted accounting principles.

Our audits were made for the purpose of forming an opinion on the basic financial statements taken as a whole. The supplemental schedules of assets held for investment purposes and reportable transactions are presented for the purpose of additional analysis and are not a required part of the basic financial statements, but are supplementary information required by the Department of Labor’s Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. The supplemental schedules are the responsibility of the Plan’s management. The supplemental schedules have been subjected to the auditing procedures applied in the audits of the basic financial statements and, in our opinion, are fairly stated, in all material respects, in relation to the basic financial statements taken as a whole.

/s/ KPMG LLP

Kansas City, Missouri
June 25, 2004

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COMMERCE BANCSHARES PARTICIPATING INVESTMENT PLAN
Statements of Net Assets Available for Benefits
December 31, 2003 and 2002

See accompanying notes to financial statements

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COMMERCE BANCSHARES PARTICIPATING INVESTMENT PLAN
Statements of Changes in Net Assets Available for Benefits
Years ended December 31, 2003, 2002, and 2001

See accompanying notes to financial statements

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COMMERCE BANCSHARES PARTICIPATING INVESTMENT PLAN
Notes to Financial Statements
December 31, 2003, 2002, and 2001

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Participant Accounts

Each participant’s account is credited with the participant’s contribution, the Company’s matching contribution, and an allocation of Plan earnings. The earnings allocation is based on the performance of the participant's investment fund balances. The benefit to which a participant is entitled is the vested portion of the participant's account.

Participants may make transfers between funds at any time upon notification to the Plan. Participating employees may transfer, at any time, the value (in 1% increments) of the employee’s account in any of the funds to another fund offered by the Plan. Participants are allowed to make investment fund transfers once during each calendar month.

Participant Loans

A participant may borrow from the Plan amounts collateralized by the vested portion of his or her Plan account. These loans may not exceed the lesser of $50,000 or 45% of the participant’s vested account balance (excluding employee stock ownership account balances). The loans are repaid through payroll deductions over terms which are based upon the amounts borrowed and normally do not exceed five years. Interest rates charged on participant loans approximate current market rates at the date of the distribution. The participant may continue to make contributions to the Plan throughout the term of the loan.

Administrative Expenses

Certain administrative functions are performed by officers or employees of Commerce Bancshares, Inc. (the Company). No such officer or employee receives compensation from the Plan. All costs and expenses incurred in administering the Plan, other than brokerage commissions incurred in connection with purchases and sales of stock, are paid by the Company.

Distributions

Distributions of vested account balances are available upon termination, subject to the approval of the plan administrator, retirement at or after age 65, death or permanent and total disability. Distributions are made in lump sum amounts to designated beneficiaries and joint survivors.

Contributions to the Plan prior to 1995 were made on either a pre-tax basis or an after-tax basis. After-tax participant and employer contributions (attributable to participant after-tax contributions) and related accumulated earnings are fully vested and available for distribution after seven full years. Participants are vested immediately in their contributions plus actual earnings thereon, however, only upon termination of employment are participants entitled to receive their pre-tax contributions and accumulated earnings thereon. If participants have three or more full continuous years of defined service at the date of employment termination, they may receive full value of their interest in employer pre-tax contributions and accumulated earnings thereon.

Forfeitures

Each participant is 100% vested in employer contributions upon death, disability or attainment of age 65 while still employed by the Company. Forfeitures are based on the nonvested portion of the employer contribution upon employee termination. Forfeited amounts are applied as a reduction of contributions by the Company or by participating subsidiaries. Forfeitures were used to reduce the Company contribution by $112,718 in 2003 and $87,525 in 2002. The year end balance of unallocated forfeitures available to offset future Company contributions amounted to $5,058 and $1,865 at December 31, 2003 and 2002, respectively.

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     During 2003, 2002, and 2001 the Plan’s investments appreciated (depreciated) in value as follows:

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Schedule 1

COMMERCE BANCSHARES PARTICIPATING INVESTMENT PLAN
Item 27a — Schedule of Assets Held for Investment Purposes
December 31, 2003

* - Related party

** - In accordance with instructions to the Form 5500, the Plan is no longer required to disclose the cost component of participant-directed investments.

See accompanying report of independent registered public accounting firm.

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Schedule 2

COMMERCE BANCSHARES PARTICIPATING INVESTMENT PLAN
Schedule of Reportable Transactions
Year ended December 31, 2003

* Related party

See accompanying report of independent registered public accounting firm.

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EXHIBIT INDEX