AIM: To determine the effect of a methanolic extract of Withania somnifera (L.) Dunal roots on sexual competence of male rats. METHODS: Male rats were orally administered 3000 mg.kg-1.day-1 of root extract for 7 days. Their sexual behaviour was evaluated 7 days prior to treatment, day 3 and 7 of treatment, and day 7, 14 and 30 post-treatment by pairing each male with a receptive female. RESULTS: The root extract induced a marked impairment in libido, sexual performance, sexual vigour, and penile erectile dysfunction. These effects were partly reversible on cessation of treatment. These antimasculine effects are not due to changes in testosterone levels or toxicity but may be attributed to hyperprolactinemic, GABAergic, serotonergic or sedative activities of the extract. CONCLUSION: Use of W. somnifera roots may be detrimental to male sexual competence.