The effects on testes and semen characteristics were studied in the rabbit after a single dose administration of the chemotherapeutic agent ifosfamide. Sexually mature male rabbits received a single intravenous injection of either 0, 60, 90, 120, or 240mg/kg body weight ifosfamide. Two phases of experimentation were conducted, lasting 1 and 18 weeks, respectively, at the end of which half of the animals from each treatment group were euthanized. Reproductive organs weighing, as well as testicular qualitative and quantitative histological examinations were performed 1 and 18 weeks post-treatment, while semen quality and libido were evaluated on a weekly basis. A decrease in the paired testes weight (90, 120, and 240mg/kg groups) and the accessory sex glands weight (240mg/kg group) were noted 1 week post-treatment. Although no histopathologic lesions or significant changes in the quantitative histologic examination were observed, semen quality examination revealed transient oligospermia (60, 90, 120, and 240mg/kg groups), teratozoospermia (120 and 240mg/kg groups), and asthenozoospermia (240mg/kg group), which returned to normal by the 6th (60 and 90mg/kg groups), 7th (120mg/kg group), or 8th week after treatment (240mg/kg group). Libido remained normal. The results suggest that ifosfamide, at a single dose, causes transient and dose-dependent depression of spermatocytogenesis (240mg/kg), spermiogenesis (60, 90, and 120mg/kg), and sperm maturation in the epididymis (240mg/kg).