This study investigated the effect of traumatic brain injury on the development of posttraumatic stress disorder (PTSD). Subjects were 107 motor vehicle accident survivors including 38 individuals who were diagnosed with posttraumatic stress disorder (PTSD). Neuropsychological testing was administered to all subjects during an initial diagnostic evaluation. Results showed that subjects who had lost consciousness during their MVA had greater impairment on speed dependent tests and delayed recall of verbal material. Subjects who suffered traumatic brain injury (TBI) were also found to have developed PTSD as often as those who had not reported TBI. Implications for future research and clinical utility are discussed.