For 10 of his 17 years in the Congress, from 1995 to 2005, Cox served in the House Majority Leadership as Chairman of the House Republican Policy Committee, the fifth-ranking elected leadership position (behind the Speaker, the Majority Leader, the Majority Whip, and the Chair of the House Republican Conference). He was Chairman of the House Committee on Homeland Security, and also Chairman of the Select Committee on U.S. National Security that produced the Cox Report, an indictment of Chinese espionage and of security failures at several U.S. national laboratories.