The effects of substance abuse on the cause, severity, and recurrence of traumatic brain injury in 322 admissions to a large rehabilitation inpatient facility are explored. Study patients tended to be young and predominantly male. Few had completed high school and a significant minority had a history of cerebral dysfunction. Patients tended to have moderate to severe closed head injuries. Motor vehicle crashes were the most common cause of injury, but patients reporting drug or drug and alcohol abuse were more likely to sustain violent injuries (e.g., gunshot wounds).