The effects of ovarian hormones on beta-adrenergic receptor-mediated responses in female rabbit detrusor smooth muscles were investigated. Ovariectomized mature female New Zealand white rabbits were untreated or treated with estrogen and/or progesterone for 2 weeks. The contractile responses to carbachol and KCl in the detrusor strips were not significantly different in all groups. As compared with dobutamine and GS-332, isoproterenol and procaterol significantly relaxed the detrusor strips derived from all groups on KCl-induced tonic contractions. Combined with estrogen treatment, isoproterenol, procaterol and GS-332 caused a significant increase in this muscle relaxation. Furthermore, estrogen treatment caused a significant increase in relaxation as a result of forskolin and the cyclic AMP (cAMP) production that was induced by isoproterenol, procaterol and GS-332. However, estrogen treatment did not affect the relaxant response to dibutyryl cyclic AMP. Progesterone treatment did not affect beta-adrenergic receptor-mediated responses. These results suggest that estrogen treatment causes the increased relaxant responses mediated by beta2- and beta3-adrenergic receptor subtypes, which may be related to the increased cAMP content in female rabbit detrusor smooth muscles.