Abstract: Intraperitoneal injection of anisodamine (Ani) 0.5～10 mg/kg delayed the latent period and shortened the duration of arrhythmia elicited by adrenaline in rabbits, and by aconitine or BaCl₂ in rats. The drug was also found to increase markedly the ouabain dosage necessary to induce ventricular premature beats, ventricular tachycardia, ventricular fibrillation and cardiac arrest in guineapigs. In mice given Ani 5～10 mg/kg ip, the incidence of Ach-CaCl₂ induced ventricular fibrillation (or flutter) was decreased. The incidence of CaCl₂ arrhythmia induced in rats was also decreased by prior administration of the drug.