We studied 980 patients with a first episode of unstable angina or myocardial infarction (MI), to examine age-related differences in risk factors and in-hospital complications and mortality. Of the total group, 52.9% were over 60 years of age and 24.3% over 70 years. The proportion of females rose with increasing age, as did the proportion of ex-smokers, while the proportion of current smokers fell. Age correlated negatively with total cholesterol levels, and positively with high-density lipoprotein cholesterol levels. The proportion of hypertensives rose with age, as did in-hospital systolic, but not diastolic, blood pressure. Older patients were more likely to have diabetes, and to have had chronic angina. There was no relation between age and either size or site of infarction. the proportion admitted with unstable angina fell with age, and, among infarctions, the proportion developing complications rose. Mortality rose from 3.1% in the under 60 subjects to 20.0% in those over 70. Cardiogenic shock tended to become more lethal with advancing age, but the outcome of ventricular fibrillation was not influenced by age. With the current aging coronary care population, management and secondary prevention methods derived from studies confined to younger subjects may be inappropriate.