One single silastic capsule containing nomegestrol acetate, Uniplant, was inserted subcutaneously in 100 women of reproductive age who desired to avoid conception. Insertions and removals of the capsules were made in the gluteal region following intracutaneous local anesthesia with 2% procaine. Eighty women completed one year of use. Eleven women bore the implant for 6-11 months. A total of 1,085 women-months were recorded. One pregnancy occurred, resulting in a Pearl Index of 1.1. Bleeding episodes similar to menstruation occurred in all women but the degree of regularity varied from subject to subject. Amenorrhea developed in the range of 14-18% during the first six months of use but declined to less than 10% during the last six months. Menorrhagia likewise was higher in the first six months (18% in the first month) but fell to less than 10% during the last six months. Spotting was 5% or less. Of the twenty women who did not complete one year of use, nine discontinued because they found other methods were either more practical or less revealing. Three discontinued because of bleeding irregularities, three desired to become pregnant, one became pregnant. Other complaints included dizziness, headache, increased blood pressure, loss of libido, painful breasts and nausea. Over half of the women indicated their desire to continue using the single implant as a contraceptive.