Fifty subjects with a history of traumatic brain injury (TBI) and/or substance use, completed neuropsychological measures of short and long term verbal and visual memory, information processing, motor speed and co-ordination, executive functioning, and malingering. All subjects performed below norms on tests of verbal memory and verbal abstract thinking, but overall no differences were found due to either severity of TBI or level of substance use. Maori subjects obtained the lowest scores on tests of verbal ability, but also reported higher rates of TBI and substance use, which is presumed to account for this result. In conclusion, prison populations seem to have disproportionately high rates of TBI, recurrent TBI, and substance use, compared to the general population. Further, there are a group of individuals who have experienced both TBI and substance abuse, with associated impairments in verbal memory and learning, abstract thinking, and who report problems with general memory and socialization. These difficulties may affect functioning both in prison and following release.