All 32 teams qualified for the European Cup entered in the first round.
The team that scored more goals on aggregate over the two legs advanced to the next round.
If the aggregate score was level, the away goals rule was applied, i.e. the team that scored more goals away from home over the two legs advanced.
The away goals rule would be again applied after extra time, i.e. if there were goals scored during extra time and the aggregate score was still level, the visiting team advanced by virtue of more away goals scored.
If no goals were scored during extra time, the tie was decided by penalty shoot-out.
The draw for the first round was held on 11 July 1991 in Geneva, Switzerland.