The pre- and postinjury patterns of alcohol and illicit drug use of 87 persons with traumatic brain injury ages 16 to 20 were examined. Follow-up data were collected at two time intervals averaging 8 and 28 months postinjury. A comparison with large-sample studies revealed that patients had preinjury drinking patterns similar to those in the general population. A review of data provided evidence of a decline in alcohol use at initial follow-up; however, preinjury and second follow-up alcohol use patterns were similar. Analyses suggested that drinking quantity and frequency increased over time, perhaps eventually returning to postinjury levels. A review of the literature and the findings of the present investigation indicate that men and persons with a history of preinjury heavy drinking are at greatest risk for long-term alcohol abuse postinjury. Postinjury illicit drug use rates remained relatively low, falling below 10% at both follow-up intervals. Among persons taking prescribed medications, 17% reported moderate or heavy drinking at second follow-up.