The board overseeing the Smithsonian Institution will review the institution's recent contract to develop an on-demand cable television channel with Showtime Networks, the Smithsonian's top executive said yesterday. The decision came after a congressional subcommittee that oversees the Smithsonian's financing asked in a letter for a review ''to determine whether it violates the spirit if not the letter of the Smithsonian Trust.''

The contract for the television channel, which aims to develop and broadcast roughly 100 hours of programming a year drawing on the Smithsonian's collections and its curators, has been criticized by documentary filmmakers and historians as restricting access to the Smithsonian's public collections.

The letter, signed by the chairman and ranking minority member of the House Appropriations subcommittee on interior, environment and related agencies, also asks the Smithsonian to organize a process to gather public testimony on future business deals that affect access to its collections.

The letter expands the debate that arose last month after Smithsonian Business Ventures contracted with Showtime to create the Smithsonian on Demand television channel. Under that deal commercial filmmakers who want to make ''more than incidental'' use of Smithsonian archives or curators will have to receive approval from the new venture, which will essentially have the right of first refusal to the works.

Responding to the Congressional inquiry in a letter yesterday, Lawrence M. Small, the secretary of the Smithsonian, vowed to have the institution's board review the deal, which he also defended as ''entirely consistent with the institution's mission.''

''The fear that the Smithsonian is curtailing or constraining the work of historians and documentary researchers seeking to use the collections is unfounded,'' Mr. Small wrote. The deal applies only to commercial producers who aim to create programs that will be sold to commercial distributors.

Access to the collections, which are publicly financed, by news and educational organizations will not be affected by the deal, he said. The Smithsonian business division previously signed a similar agreement with the HarperCollins publishing house to create books related to Smithsonian content.

The Congressional letter, dated Thursday, said the deal could ''appear to essentially sell access to Smithsonian resources.'' It asks the board to ''consider changes to the contract'' that would guarantee that it does not bar access to ''commercial filmmakers who we believe have the right to reasonable access to the collections and staff.''

The Smithsonian is overseen by a 17-member Board of Regents that includes the institution's chancellor, Chief Justice John G. Roberts Jr.; Vice President Dick Cheney; three senators and three members of the House of Representatives; and nine members from foundations and the business and educational worlds. The board, which meets three times a year, in January, May and September, previously approved the deal with Showtime.

But the deal has drawn criticism, including a letter signed by more than 200 filmmakers, television executives and academics. The letter was put together by the Center for American Progress, a liberal research organization.

The congressional letter is signed by Representatives Charles H. Taylor, Republican of North Carolina and the subcommittee chairman, and Norm Dicks, Democrat of Washington and the subcommittee's ranking minority member. The subcommittee is considering an appropriations bill that includes financing for the Smithsonian.