We studied 172 episodes of bacteremia attributed to nosocomial pneumonia in 168 patients, observed in the 4 major hospitals of a single metropolitan area over a 5-yr period. Overall mortality for these patients was 58%. Deaths attributed directly to nosocomial pneumonia occurred almost exclusively in patients with serious and largely irreversible underlying diseases. These data confirm the high mortality associated with endemic hospital-acquired pneumonia. Although some deaths appear to be preventable, primarily by measures designed to reduce the risk of aspiration, analysis of the data herein raises doubts whether overall mortality can be significantly reduced by currently available measures.