Vehicle-related trauma is a common mechanism of injury in elderly (age > or = 65 years) trauma patients. Several hospital-based studies have shown that patients with pedestrian injury have a higher mortality compared with those with motor vehicle collision (MVC) injury partially because of older patients found in the former group. In addition the injury patterns also differ significantly between these two mechanisms of vehicle-related trauma. The purpose of the present study is to compare the demographics, injury severity, injury patterns, and outcomes of elderly patients with pedestrian injury admitted to a surgical intensive care unit (SICU) of a Level I trauma center between January 1, 1994 and December 31, 2000 with those admitted with MVC injury. During the study period there were 187 elderly patients admitted to the surgical intensive care unit with vehicle-related injury. Fifty-one per cent of the patients had MVC injury. Patients were divided into two groups based on their mechanisms of injury (pedestrian vs MVC) for comparison. There was no difference in the mean age and gender between the two groups. Injury Severity Score, admission Simplified Acute Physiology Score, and mortality were significantly higher in the pedestrian group compared with the MVC group. Using logistic regression analysis three factors were found to be independently predictive of mortality: Simplified Acute Physiology Score, intracranial hemorrhage with mass effect on CT scan, and cardiac complications.