Since there is concern that the potentially useful antihypertensive combination of verapamil and propranolol might lead to adverse cardiovascular responses, we have investigated its effects, not only on blood pressure, but also on electrocardiographic and echocardiographic variables. Fourteen hypertensive patients participated in a double-blind, randomized, crossover comparison of verapamil 360 mg, propranolol 240 mg, verapamil 360 mg + propranolol 240 mg, and placebo, each given for 4 weeks. The antihypertensive effect of verapamil + propranolol was greater than that of either drug alone. Pulse rate was reduced by propranolol but not verapamil. However, addition of verapamil to propranolol led to further reduction in pulse rate. The PR interval was prolonged by verapamil + propranolol when compared with all other treatments. The active drugs increased ventricular dimensions and the effect of the combination was statistically significant. Thus, verapamil + propranolol is an effective antihypertensive combination, but heart rate, atrio-ventricular conduction and left ventricular function may be affected adversely, necessitating careful monitoring of therapy.