Between August 1983 and August 1992, 1995 women aged 20-43 years were fitted with 2736 copper intrauterine contraceptive devices (MLCu250, MLCu375, Nova-T, Gravigard, Anticon). Insertion of the IUD was performed during menstruation by a skilled team of gynecologists. The women were instructed to self-check the IUD tail after each menstrual period. All the women were examined after one month and were followed-up every six months. The 1995 acceptors accumulated a total use of 69,350 months. During this period 39 accidental pregnancies occurred (Pearl Index 0.62, cumulative net pregnancy 1.95 per 100 women). Thirty-six pregnancies were intrauterine and three were ectopic. Most of the accidental pregnancies occurred during the first 12 months of use. The pregnancy rate of IUD users was negatively correlated with age. It is concluded that fitting the Cu-IUD intramenstrually, teaching the user to self-check herself and having frequent re-examinations seems to decrease the pregnancy rate in Cu-IUD users.