The GnRH analogue deslorelin, in long-acting biocompatible implants, was used as a contraceptive in 31 cheetahs (13 females and 18 males), 21 African wild dogs (15 females and 6 males), 10 lionesses and four leopards (three females and one male). A dose of 12 or 15 mg deslorelin was administered to lions, whereas 6 mg deslorelin was administered to the other species. Monitoring consisted of observations, measurement of plasma progesterone and testosterone concentrations, vaginal cytology and evaluation of semen and sex organs. Deslorelin induced contraception in lionesses for 12-18 months, and in female cheetahs and leopards for a minimum of 12 months after treatment. Two male cheetahs had no viable spermatozoa or detectable plasma testosterone 21 months after treatment with deslorelin. Female wild dogs responded less consistently and one bitch conceived 4 weeks after implantation. However, in nine bitches, mating could be postponed until the next breeding season. Male dogs responded consistently and the contraception was effective for approximately 12 months. Although lionesses and cheetahs may become attractive to males for a few days after treatment, mating was not observed. No side-effects or behavioural changes were noted, indicating that deslorelin is a safe drug to use for the contraception of the species described. Males remain fertile for the first 6 weeks after the insertion of implants and should be separated from cyclic females during this period.