We investigated the underlying mechanisms of penehyclidine hydrochloride (PHC), a novel selective anticholinergic drug on isolated rat uterus. The method of radio-immunity assay was further employed to determine cyclic adenosine mono phosphate (cAMP) levels in isolated rat uterus for comparing with selective effect on muscarinic receptor subtypes. In the assay, PHC could decrease the content of cAMP in isolated rat uterus, but the difference was not statistically significant at dose of 10 mumol/L. In conclusion, our results suggested that PHC has no or poor effect on M(2) receptor subtypes in isolated rat uterus.