Between September 1, 1981, and August 31, 1982, all patients with suspected or confirmed pneumonia among the 46,979 inhabitants of four municipalities in the province of Kuopio, Finland, were reported to a pneumonia register by their attending physicians. In addition, two study pathologists reported all cases of pneumonia found at autopsy, and two permanent registers were checked for retrospective identification of patients. Chest radiographs were obtained from 97% of all patients. The final diagnosis was based on radiologic or autopsy criteria. A total 546 patients (323 males and 223 females) had community-acquired pneumonia; of these, 37% were less than 15 years of age, and 31% were 60 years of age or older. Nineteen percent of the patients had defined chronic conditions, and 42% were admitted to hospital. The case fatality rate was 4%. The overall incidence of community-acquired pneumonia per 1,000 inhabitants per year was 11.6 (13.9 in males, 9.4 in females). The age-specific incidence per 1,000 inhabitants per year was as follows: age < 5 years, 36.0; age 5-14 years, 16.2; age 15-59 years, 6.0; age 60-74 years, 15.4; and age > or = 75 years, 34.2.