Abstract: The guinea-pig atria was used to study the effects of berbamine on amplitude of contraction, automaticity, ERP and intensity duration curve. The effects of berbamine on adrenaline-induced automaticity was compared with verapamil. It was found that berbamine markedly inhibited the force of contraction of guinea-pig atria, prolonged the ERP, attenuated adrenaline-induced automaticity, but the intensity duration curve of guinea-pig atria was not influenced. Propranolol competitively antagonized the effects of isoproterenonl. Berbamine and verapamil antagonized isoproterenol, but in a noncompetitive manner.Berbamine and verapamil shifted the calcium dose-response curve to the right, and acted as non-competitive antagonists. The PD₂′ of berbamine was 3.92 and that of verapamil was 4.43. Berbamine also shifted the histamine dose-response curve to the right, but in a non-competitive manner.