Abstract: The affinities of L-n-butyl-scopolamine，DL-n-butyl-scopolamine and atropine for the M-cholinergic receptors of rat uterus were compared using radioligand binding assay．Results showed that the affinity of L-n-butyl-scopolamine for the M-receptors was similar to that of DL-n-butyl-scoplamine．but lower than that of atropine．In isolated rat uterus．L-and DL-n-butyl-scopolamine were found not to influence the automatic contraction but antagonize the contraction induced by acetylcholine with nearly the same PA₂，although the PA₂ of both compounds were still lower than that of atropine．Therefore，no difference between L-and DL-n-butyl-scopolamine in either biological activity or receptor affinity was observed．