In thirteen patients with coronary insufficiency and angina pectoris the therapeutic effects of verapamil, 80 mg three times/day and practolol, 100 mg three times/day, were compared and tested against placebo in a double-blind cross-over fashion. Verapamil proved to be the most efficient drug as regards attack frequency and glyceryl trinitrate consumption as well as physical working capacity, bringing about a statistically significant increase of the exercise tolerance as compared to placebo after a treatment period of four weeks. Verapamil is a good alternative to beta-blockers in the prophylactic treatment of angina. Possible modes of action of verapamil in angina pectoris are discussed. The study had to be interrupted because of the reports of side effects of practolol, explaining the small number of patients.