Twenty patients with angina pectoris received propranolol hydrochloride at two dosage levels and placebo in a double-blind trial. The lower dosage of propranolol hydrochloride (80 mg/day) failed to reduce the frequency of anginal attacks. The higher dosage of propranolol hydrochloride (160 mg/day), however, decreased the number of daily pain episodes in 17 patients and the amount of nitroglycerin consumed (P <0.02). No correlation was found between the response to the drug and the left ventricular end diastolic (LVED) pressure measured prior to the drug trial. Propranolol was effective also in patients with severe coronary disease judged from coronary angiography, but there was a trend toward better results in patients with less severe involvement of the coronary arteries. Exercise tolerance became greater on the regimen of propranolol. Adverse effects were never severe enough to warrant stopping the trial.