Acinetobacter calcoaceticus var anitratus, a nonfermentative grampnegative bacillus, has been infrequently reported as a cause of community-acquired pneumonia. In this paper we describe the course of six recent patients with community-acquired, bacteremic pneumonia due to this organism and review the six previously reported cases. Our experience suggests this organism is a more common cause of community-acquired pneumonia than previously thought. Acinetobacter pneumonia occurs in older persons with chronic disease, especially alcoholism. It is a fulminant illness with respiratory distress, hypoxemia, leukopenia and shock. Chest roentgenograms reveal a lobar or bronchopneumonic infiltrate which often becomes bilateral within 24 hours of admission to the hospital. Pleural effusions are common. The mortality rate is 43 per cent. Factors that predict a fatal outcome are granulocytopenia, empyema and therapy with inappropriate antibiotics. Therapy with appropriate antibiotics, especially carbenicillin and an aminoglycoside, increases survival.