We carried out a retrospective cross-sectional study on 500 women in Isfahan who started taking combined oral contraceptives (COCs) during the period 21 March 1995–20 March 1997. The cumulative continuation rate fell from 77% to 12% over 60 months. The most common reason for discontinuation was side-effects. There was a significant correlation between side-effects and cumulative COC continuation rate (P < 0.05). The lowest rate was seen in women reporting nausea or vomiting. Women who are interested in COCs should receive extensive counselling about the possible side-effects and should be helped to find a method of birth control suited to their temperament and physiology.