Four hundred patients who were admitted over the last three years with myocardial infarction were questioned about the presence and pattern of angina before its onset. Two hundred and twenty-four (56 per cent) patients had angina before their infarction; 184 (46 per cent) had the unstable pattern of angina. That such a high proportion of patients experience unstable angina as a prodromal symptom makes it possible that myocardial infarction could be prevented in some of these patients. Patients with previous angina had a higher incidence of subendocardial infarction than patients without angina (stable or unstable) (p less than 0.01). In-hospital prognosis was better in patients with chronic or unstable angina than in patients without angina (p less than 0.05).