The Senate Internal Security Subcommittee (SISS) was created by S. 366, approved December 21, 1950, to study and investigate espionage, sabotage, and the protection of the internal security of the United States. The subcommittee published over 400 volumes of hearings and numerous reports, documents, and committee prints. 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.