The β-Blocker Heart Attack Trial (BHAT) was a National Heart, Lung, and Blood Institute-sponsored, multicenter, randomized, double-blind, and placebo-controlled trial designed to test whether the regular administration of propranolol hydrochloride to men and women who had experienced at least one myocardial infarction would result in a significant reduction in total mortality during a two- to four-year period. During a 27-month interval, 3,837 persons between the ages of 30 and 69 years were randomized to either propranolol (1,916 persons) or placebo (1,921 persons), five to 21 days after the infarction. Depending on serum drug levels, the prescribed maintenance dose of propranolol hydrochloride was either 180 or 240 mg/day. The trial was stopped nine months ahead of schedule. Total mortality during the average 25-month follow-up period was 7.2% in the propranolol group and 9.8% in the placebo group. Arteriosclerotic heart disease (ASHD) mortality was 6.2% in the propranolol group and 8.5% in the placebo group. Sudden cardiac death, a subset of ASHD mortality, was 3.3% among the propranolol patients and 4.6% among the placebo patients. Serious side effects were uncommon. Hypotension, gastrointestinal problems, tiredness, bronchospasm, and cold hands and feet occurred more frequently in the propranolol group. Based on the BHAT results, the use of propranolol in patients with no contraindications to β-blockade who have had a recent myocardial infarction is recommended for at least three years.