Two analogues of verapamil, ronipamil and anipamil, were tested for their ability to reduce arrhythmias induced by occlusion of the left anterior descending coronary artery in conscious rats. Only anipamil (50 and 150 mg kg-1 orally) produced a statistically significant reduction in arrhythmias; it was most effective against ventricular fibrillation. Ronipamil at the same doses had limited antiarrhythmic actions. Only anipamil delayed the development of ECG signs of ischaemia, while both drugs reduced the magnitude of such changes. Anipamil has a more favourable ratio of antiarrhythmic to hypotensive effects when compared with verapamil.