In reality it oversaw the operations of the Committee and made all major policy decisions, which were then passed down through the Central Committee, the Supreme Soviet and the Party Congress. Its control extended from the Party and into government because Party personnel held all key government posts and party discipline therefore insured that Politburo policy was implementated by all government organizations.
Members of the Politburo were selected informally by current members through a secret process. The selection was rubber-stamped by the Central Committee. The Politburo had both full and candidate (non-voting) members. The actual size of the Politburo varied, but it usually consisted of fourteen full and eight candidate members. Although it had no formal head, it was always led by the General Secretary of the Party, who was also often head of the Central Committee. In practice the most powerful Politburo members were those who were also members of the Secretariat of the CPSU Central Committee, the General Secretary being the leader of this group.Those who were members of only one of these two bodies had less influence.
From 1952 to 1966 the Politburo was called the presidium.
In 1990 the 28th Party Congress agreed to transfer the powers of the Politburo to parliament and the Politburo ceased to exist in August 1991.