The case history of two patients with symptomatic ventricular tachycardia is described. The first patient with systolic narrowing of a segment of the left anterior descending artery did not show any improvement on class I and III antiarrhythmic drugs. Oral verapamil suppressed the arrhythmia which showed some features of triggered activity. Cessation of the drug resulted in symptomatic recurrence. The second patient presented with a sustained ventricular tachycardia showing the morphology of right bundle branch block and left axis deviation. During electrophysiologic study the tachycardia was not inducible after oral verapamil. No definite conclusion on the mechanism of the arrhythmia could be drawn, nor on the mechanism of the antiarrhythmic action of verapamil in the first patient. Appropriate techniques to prove the efficacy of verapamil are needed in patients when it is given for chronic treatment of ventricular tachycardia.