This report describes surveillance of pneumonia in an entire community during a 2-year interval. The study, which was performed on the Navajo reservation, included those who sought care for defined clinical manifestations and who showed pulmonary infiltrate(s) on roentogenographic examination. Approximately 10 bouts of pneumonia per 1,000 persons required hospitalization, and an equal number were treated at home each year. Rates were highest at the extremes of age and were higher among males. Multiple attacks were observed in 14.5 per cent of infants and children and in 7.6 per cent of adults. Most illnesses were associated with pneumococci. The proportions of these illnesses, however, were smaller among hospitalized children than among adults. Pneumococcal bacteremia was uncommon in infants and children. Most pneumococcal serotypes isolated are included in currently proposed antipneumococcal vaccines. The 2-year case fatality rate was 2.2 per cent. None of those who dided had been previously well. Factors associated with multiple occurrences need further study. Efforts at prevention should be directed to life's extremes, especially to those already infirm.