Eleven cases of blood culture-positive, community-acquired pneumonia due to the human commensal Acinetobacter baumannii were studied in Darwin in the Northern Territory of Australia during the 10-year period from March 1981 through February 1991. Demographic risk factors included male gender, age of greater than 45 years, and Aboriginal ethnic background. Multiple clinical risk factors, including cigarette smoking, alcoholism, chronic obstructive airway disease, and diabetes mellitus, were noted in all cases and contributed to the high mortality (64%). In all cases pneumonia was clinically fulminant. A fatal outcome was strongly associated with inappropriate initial antibiotic therapy. All tested isolates of Acinetobacter were sensitive to gentamicin and resistant to cefotaxime. The 34 previously reported cases of community-acquired acinetobacter pneumonia are reviewed, and appropriate therapeutic regimens are identified.