The process of assigning committees differ from chamber to chamber and party to party. In the House, members are assigned to only one or two standing committees. House committees are usually larger than those in the Senate. The size of Senate committees is written into the rules of the chamber, while House committee size is decided informally by the party leaders. Party leaders assign new members to specific committees, rewarding or punishing members for past actions.
Subcommittees can be as important, or more important than full committees.
For example, in 1995, the Telecommunications and Finance Subcommittee of the House Commerce Committee was responsible for a major securities reform bill, and the Telecommunications Reform Bill. In the House, the chairmen of the subcommittees are elected by a vote of the majority party members on the full committee. The majority members of a committee also decide the number and scope of the subcommittees. Until the reforms of the 1970s, these powers were reserved for the committee chairman. In the Senate, subcommittee chairmen are selected by a less formal process of discussions between the committee chairman and the majority party members.