Contraceptive efficacy, reversibility and toxicity, if any, of the benzene, chloroform and ethyl acetate chromatographic fractions of the chloroform extract of the seeds of Carica papaya have been investigated in adult male rabbits at a dose regimen of 50 mg/animal/day for 150 days of treatment. Body weight, semen analysis, hematology, serum clinical biochemistry and the fertility status of control and treated animals were evaluated. Chloroform and ethyl acetate chromatographic fractions did not produce appreciable changes in these parameters. However, the benzene chromatographic fraction resulted in uniform azoospermia after 15 days of treatment, which was maintained for the remainder of the 150-day observation period. The levels of fructose, glycerophosphocholine, acid phosphatase and lactate dehydrogenase in the seminal plasma were within the control range. Hematology and the serum clinical parameters showed no appreciable changes, indicating lack of toxicity. The libido of the treated animals was normal and the fertility rate was zero. Complete normalcy of altered parameters was observed 60 days following withdrawal of treatment. It is concluded that the benzene chromatographic fraction of the chloroform extract of the seeds of Carica papaya possesses reversible male contraceptive potential and the effects appear to be mediated through the testis.