Aim:To investigate the effect of methanol extract of Ricinus communis seed(RCE)on male rats reproductivefunctions.Methods:Thirty-two male albino rats were divided into four groups.Groups 1,2 and 3 were gavagedwith 0.2 mL of 2.5% tween 80(RCE vehicle;control)or 20 mg/(kg·d)and 40 mg/(kg·d)of RCE,respectively,for30 days,and group 4 was also gavaged with 40 mg/(kg·d)of RCE,but was allowed a recovery periold of 30 days.Five untreated female rats were cohabited with male rats in each group from day 25 of RCE treatment for 5 days,except group 4,where cohabitation began on day 25 of the recovery period.All male rats were sacrificed 24 h afterthe experiments.The female rats were laparatomized on day 19 of pregnancy and the number and weight of litterswere recorded.Results:There was a significant decrease(P<0.01)in the weight of the reproductive organs,sperm functions and serum levels of testosterone in RCE treated rats.There was disorganization in the cytoarchitec-ture of the testes,disruption of the seminiferous tubules and erosion of the germinal epithelium.The number andweight of litters of rats in groups 2 and 4 decreased significantly(P<0.05)but no changes were observed in group3.RCE caused no changes in liver,kidney,heart or body weights in male rats.Conclusion:RCE has a reversiblenegative impact on male reproductive functions,which appears to be mediated via gonadal disruption in testosteronesecretion.(Asian J Androl 2006 Jan;8:115-121) Aim: To investigate the effect of methanol extract of Ricinus communis seed (RCE) on male rats reproductive functions. Methods: Thirty-two male albino rats were divided into four groups. Groups 1, 2 and 3 were gavaged with 0.2 mL of 2.5% tween 80 (RCE vehicle; control) or 20 mg / (kg · d) and 40 mg / (kg · d) of RCE, respectively, for 30 days, and group 4 was also gavaged with 40 mg / (kg · d) of RCE, but was allowed a recovery periold of 30 days. Five untreated female rats were cohabited with male rats in each group from day 25 of RCE treatment for 5 days, except group 4, where cohabitation began on day 25 of the recovery period. were sacrificed 24 h afterthe experiments. female rats were laparatomized on day 19 of pregnancy and the number and weight of litterswere recorded. Results: There was a significant decrease (P <0.01) in the weight of the reproductive organs, sperm functions and serum levels of testosterone in RCE treated rats. There was disorganization in the cytoarchitecture of the testes, disrupt ion of the seminiferous tubules and erosion of the germinal epithelium.The number and weight of litters of rats in groups 2 and 4 decreased significantly (P <0.05) but no changes were observed in group 3. RCE caused no changes in liver, kidney, heart or body weights in male rats. Conlusion: RCE has a reversible negative impact on male reproductive functions, which appears to be mediated via gonadal disruption in testosteronecretion. (Asian J Androl 2006 Jan; 8: 115-121)