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 Bucureşti on 19 January 1964: Steaua Bucureşti - Galatasaray 57-56.
**Benfica withdrew before the first leg and Legia Warsaw received a forfeit (2-0) in both games.
***PUC couldn't 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 quarter finals
CSKA Moscow (title holder) withdrew before the competition. The "official" explanation given by the Soviet Basketball Federation was to prepare the Olympic Games.