The United States Senate's Special Subcommittee to Investigate the Administration of the Internal Security Act and Other Internal Security Laws, 1951–77, known more commonly as the Senate Internal Security Subcommittee (SISS) and sometimes the McCarran Committee, was authorized by S. 366, approved December 21, 1950, to study and investigate (1) the administration, operation, and enforcement of the Internal Security Act of 1950 (Pub. L. 81–831, also known as the McCarran Act) and other laws relating to espionage, sabotage, and the protection of the internal security of the United States and (2) the extent, nature, and effects of subversive activities in the United States "including, but not limited to, espionage, sabotage, and infiltration of persons who are or may be under the domination of the foreign government or organization controlling the world Communist movement or any movement seeking to overthrow the Government of the United States by force and violence". The resolution also authorized the subcommittee to subpoena witnesses and require the production of documents. Because of the nature of its investigations, the subcommittee is considered by some to be the Senate equivalent to the older House Un-American Activities Committee (HUAC).
The chairman of the subcommittee for the 82nd United States Congress was Patrick McCarran of Nevada. William Jenner of Indiana took over during the 83rd United States Congress after the Republicans gained control of the Senate in the 1952 election. When the Democrats regained control in the 84th Congress (1955–1957), James O. Eastland of Mississippi became chairman, a position he had until the subcommittee was abolished during 1977.
