In 917 patients with acute myocardial infarction (AMI) we evaluated the impact of previous angina pectoris on the prognosis. Thirty-four percent of the patients had chronic angina prior to AMI, and 22% had angina pectoris of short duration. Patients with chronic angina pectoris differed from the remaining patients having a more frequent previous history of AMI, diabetes mellitus, hypertension, and congestive heart failure. They less frequently developed a Q-wave AMI, and had smaller infarcts according to maximum serum-enzyme activity as compared with the remaining patients. They had a higher one-year mortality rate (36%) as compared with those having angina pectoris of short duration (22%), and those with no angina pectoris (26%). Their reinfarction rate was also higher (26%) as compared with that in the other two groups (15% and 9% respectively). In a multivariate analysis considering age, sex, clinical history, initial symptoms, initial electrocardiogram and estimated infarct size, previous chronic angina pectoris was not an independent risk factor for death, but was independently associated with the risk of reinfarction (P < 0.001). Among patients with a history of angina pectoris the outcome was related to medication prior to onset of AMI and at discharge from hospital. Patients in whom beta-blockers were prescribed at discharge had a one-year mortality of 13% as compared with 30% in the remaining patients (P < 0.001).