Primary objective: To identify the patient population at greatest risk for post-injury adjustment problems, the present study independently examines and compares alcohol and drug use rates in patients with traumatic brain injury (TBI) and patients with spinal cord injury. Research design: The two samples were matched with regard to age, gender and mechanism of injury. The study provides a description of post-injury use rates for each population, and describes similarities and differences between the two groups. Methods and procedures: Participants included 30 consecutive Model Systems spinal cord injury (SCI) patients seen for follow-up neuropsychological testing between October 1996-June 1999. An equivalent number of Model Systems TBI patients were matched from a larger sample comprised of 440 consecutive hospital admissions, that returned for a 1-year follow-up neuropsychological evaluation between February 1989-December 1998. All participants were treated in an urban Level I trauma centre and associated inpatient rehabilitation programmes. Information regarding patient demographics, as well as pre- and post-injury psychiatric, employment, academic, criminal, and medical history was obtained via the General Health and History Questionnaire. Main outcomes and results: With regard to post-injury alcohol use rates, persons with spinal cord injury were more likely to drink on a daily basis. Although not statistically, pre-injury drinking rates differed from post-injury rates for both groups. With regard to illicit drug use, persons with TBI differed significantly from persons with SCI. A significant difference was also noted between pre-injury drug use and post-injury drug use for both groups. Conclusions: Persons who drink post-injury are unlikely to be 'light' or social drinkers. Either people choose to abstain completely or appear to use alcohol frequently.