NORPLANT progestogen-only implant contraception provides several years of effective protection against pregnancy following a single application. It is reversible whenever desired, with return to normal fertility. Drug release and concentrations are maximal in the first month of use, when a set of six capsules releases approximately 85 micrograms/day of levonorgestrel. Release is 25-30 micrograms/day at 60 months. Circulating drug concentrations and pregnancy rates vary inversely with body weight at placement, but even among heavier women, failure rates are below those of oral contraceptives in the general population. Side-effects are most marked at the initiation of use. Disruption of normal menstrual patterns occurs in 70-80% of recipients initially. Menstrual blood loss is decreased, however, and most women experience modest increases in haemoglobin. Headache, acne, other skin or hair problems, changes of weight and of mood and abdominal pain, are the most common side-effects attributed to NORPLANT contraception. The frequency of occurrence of side-effects diminishes with increased duration of use. The comparative paucity of major side-effects, coupled with the method's convenience and effectiveness and its very long action have made NORPLANT implants highly acceptable in both developing and developed countries.