Terminalia bellerica has been used as a folk medicine in a variety of ailments including hypertension. Our aim was to investigate the possible mechanism of its blood pressure (BP)-lowering effect. The crude extract of Terminalia bellerica fruit (Tb.Cr) which tested positive for flavonoids, sterols and tannins induced a dose-dependent (10-100 mg/kg) fall in the arterial BP of rats under anaesthesia. In isolated guinea-pig atria, Tb.Cr inhibited the force and rate of atrial contractions. In rabbit thoracic aorta, Tb.Cr relaxed the phenylephrine (PE, 1 μM) and K+ (80 mM)-induced contractions as well as suppressed the PE (1 μM) control peaks in the Ca++-free medium, similar to that caused by verapamil. The vasodilator effect of Tb.Cr was endothelium-independent as it was not opposed by Nω-nitro-L-arginine methyl ester in endothelium-intact rat aortic preparations and it occurred at the similar concentration in the endothelium-denuded tissues. These results indicate that Terminalia bellerica lowers BP through Ca++ antagonist mechanism and thus provides a sound mechanistic background for its medicinal use in hypertension.