As the elderly population increases and they lead more active and healthy lifestyles, their exposure to the threats of injury multiply. Undoubtedly, the geriatric population will comprise a growing percentage of trauma patients. The role of alcohol and drug use in geriatric trauma has not been clearly defined. The purpose of this study is to determine the incidence of alcohol and illicit drug use in association with mechanism of injury in all elderly trauma patients presenting to level I and II trauma centers in the State of Illinois over 3 years. A retrospective analysis was performed on 3 years of data (January 1, 1994 to December 31, 1996), provided by the Illinois Department of Public Health as the Illinois Trauma Registry, which describes consecutive trauma patients presenting to level I and II trauma facilities in the State of Illinois. During the study period, there were a total of 134,846 trauma patient entries. Of these 32,382 (24.0%) were for patients 65 years of age or older. In those patients 65 and older, 1699 (5.2%) were tested for the presence of alcohol and 845 (49.7%) tested positive. Of the elderly patients who tested positive for alcohol, 71.8% were considered intoxicated (BAC >80 mg/dL). Urine toxicology screens were performed on 1785 (5.5%) elderly trauma patients, and 208 (11.6%) were positive. Besides alcohol, benzodiazipines and opiates were the most frequently detected drugs. For elderly patients under the influence of alcohol falls (49.5%) and motor vehicle crashes (36.7%) were the most common mechanism of injury. For geriatric patients testing negative for alcohol, motor vehicle crashes were a much more common mechanism of injury than falls (65.0% v 25.1%). Falls were a much more common cause of injury in elderly patients using alcohol than in those not using alcohol. Alcohol and substance abuse are possibly significant factors in geriatric trauma. Although only 5% of elderly trauma patients were tested for alcohol, nearly half had alcohol present on presentation to a trauma center, and the majority of these patients were intoxicated. Prospective studies are needed to determine the true incidence of alcohol use/abuse in the geriatric trauma population and the need for routine alcohol screening of these patients. Detection of alcohol abuse in elderly trauma patients could help identify individuals in need of counseling and rehabilitative treatment. It may also reduce future injuries in these patients.