Five year's experience recorded in the adult registry of a Level I trauma center was reviewed to identify all recorded complications. Patients in whom pneumonia occurred were further analyzed for associated risk factors and for potentially preventable occurrence. Of 10,001 patients, 1027 (10%) sustained a total of 1905 complications. Patients with complications were more severely injured (mean Injury Severity Score = 27.5 versus 9.6;P < 0.01). Pneumonia occurred in 392 patients and was the most frequently encountered complication. Mortality for patients with uncomplicated care was 5.8 per cent in comparison with 46 per cent for those with any complications (P < 0.001), and 30.3 per cent for the pneumonia group (P <0.05). Age >65 years, Injury Severity Score >15, Glasgow coma scale score <8, cervical spine fracture with spinal cord injury, Abbreviated Injury Scale >3 for head, chest, and abdomen regions were associated with an increased risk of pneumonia (P < 0.001). Forty-four patients who developed pneumonia (11%) presented without any risk factor. Two of five related deaths could be considered potentially preventable. We conclude that the incidence of complications related to trauma care increases with injury severity and that complications are associated with a significantly higher mortality. The frequency of pneumonia, 11 percent of which were potentially preventable, emphasizes the critical importance of infection control and aggressive pulmonary toilet in the early care of injured patients.