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23 teams. European national domestic league champions, plus the then current FIBA European Champions Cup title holders only, playing in a tournament system. The Finals were a two-game home-and-away aggregate.
*Since the aggregate score after the two legs was tied, a tie-break was played in București on 19 January 1964: Steaua București – Galatasaray 57–56.
**Benfica withdrew before the first leg and Legia Warsaw received a forfeit (2–0) in both games.
***PUC could not travel to Belgrade to play the first leg after all fights to the Yugoslavian capital were cancelled due to adverse weather. Later, FIBA decided that this tie should be played as a single game in Paris (16 January 1964).
Automatically qualified to the quarterfinals
CSKA Moscow (title holder) withdrew before the competition. The "official" explanation given by the Soviet Basketball Federation was to prepare the Olympic Games.
First leg Brno Ice rink, Brno;Attendance 11,207, also mentioned as 12,000 or 14,000 (27 April 1964) Second leg Frontón Vista Alegre, Madrid;Attendance 2,500 (10 May 1964)