The effects of berbamine (Ber, 10 mg.kg-1 iv) on ischemic ventricular tachyarrhythmia and electrophysiologic consequences in both normal and ischemic myocardia were studied in the open-chest dogs subjected to programmed electrical stimulation (PES) on 5-8 d after acute myocardial infarction. Its effects were compared with procainamide's (PA). Both drugs distinctly lengthened the QTc interval and the effective refractory period (ERP) of normal and infarct ventricular myocardium, decreased the dispersion of ERP in infarct myocardium (IDR) and the dispersion of ERP in left ventricle (VDR), and increased the diastolic excitability threshold (DET) of normal and infarct ventricular myocardium remarkably. The PES-induced ventricular tachycardia (VT) or ventricular fibrillation (VF) was prevented in 5 out of 6 dogs treated with berbamine and procainamide respectively. (Normal saline did not prevent PES-induced VT or VF). The results suggest that berbamine may be effective in preventing the onset of reentrant ventricular tachyarrhythmia after myocardial ischemic damage.