The effects of the aqueous extract of Pavetta crassipes leaves were studied on gastrointestinal and uterine smooth muscle preparations isolated from rabbit jejunum, guinea pig ileum and rat uterus. The extract produced a concentration-dependent inhibition of the spontaneous motility or elevated tone in these preparations. The inhibitory effects of the extract were not affected by pretreatment with propranolol or yohimbine, but were completely blocked by verapamil pretreatment. The results indicate the presence of biologically active substances whose action might be mediated through calcium channels. A preliminary phytochemical screening of the leaf extract of P. crassipes revealed the presence of flavonoids, tannins and anthraquinones as possible candidates for such inhibitory substances.