The BHAT trial was a double-blind, randomized trial of the effects of propranolol on survival after acute myocardial infarction. The total group numbered 3,837 patients, aged 30-69. Patients were excluded from the study if they had medical contraindications to propranolol, a history of severe congestive heart failure or asthma as an adult, or if they had or were likely to undergo cardiac surgery. Clinical and personal characteristics and ECG data, including the results of 24-hour monitoring from the baseline reference examination, were completed while patients were hospitalized prior to randomization. Patients were seen at regular intervals and a random sample of 1,000 patients had a second 24-hour monitoring at 6 weeks. Also at this visit, a psychosocial stress questionnaire was completed for 2,320 men. Patients were followed for a minimum of one and up to three years after index myocardial infarction. Official follow-up was terminated at 3 years on the recommendation of the Policy Monitoring Board. The main finding of improved survival among patients taking propranolol has been widely reported.