All cardiac admissions to coronary care unit (CCU) beds and all intensive care unit (ICU) overflow admissions in Hamilton, Ontario, a city of 375,000 people, were documented over a one-year period, 1979-80. There were 4180 such admissions, 89% of them to CCUs. In the CCUs, 22% of patients had acute myocardial infarction, 24% unstable angina and 21% other chest pain. For myocardial infarction, hospitalization rate was 224 per 100,000, hospital mortality 42 per 100,000 and 48% of all myocardial infarction deaths in the community occurred in hospital. Of all myocardial infarction patients admitted to the CCU, 69% were correctly diagnosed on admission (sensitivity) and of all the admission diagnoses of myocardial infarction, 72% were eventually found to be correct (positive predictive value). Mean values for CCU patients overall were age 62.5 years, CCU stay 2.88 days and hospital stay 9.7 days; and for acute myocardial infarction patients in CCUs, age 63.4 years, CCU stay 3.98 days and hospital stay 13.28 days. For myocardial infarction, CCU mortality was 10.9%, hospital mortality 15.2% and, with the inclusion of ICU overflow patients, hospital mortality was 17.6%. Age-specific mortality for myocardial infarction was 9.7% age 45 to 64 years, and 32.8% over 70 years.