Six patients with idiopathic paroxysmal ventricular tachycardia were investigated by external electrocardiography, intracardiac electrography and pacing, exercise testing, cardiac catheterization and coronary angiography. All had normal hemodynamics and coronary arteries. His bundle electrography proved ventricular origin in five; one had no paroxysmal ventricular tachycardia during His bundle electrography. Treatment with diphenylhydantoin, 4.2 to 8.0 mg/kg/day, and propranolol, 0.8 to 2.7 mg/kg/day, appeared effective, well tolerated therapy in three, and procainamide and propranolol in one requiring medical treatment. Abstinence from tobacco and coffee abolished paroxysmal ventricular tachycardia in one of two who required no medication. The other has no recurrence of paroxysmal ventricular tachycardia since study.