Although the cognitive effects of traumatic brain injury (TBI) have been well investigated, emotional problems are less well understood. The purpose of this study was to explore the relationship of the length of loss of consciousness (LOC) and the severity of cognitive impairment (HRNB) to personality changes after head trauma. The subjects included 320 chronic TBI patients. A multivariate analysis was conducted using HRNB (three levels), as measured by a modified Halstead-Reitan Impairment Index and LOC (four levels), as the independent variables, and 30 scales from the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) as the dependent variables. Multivariate Fs were significant for both HRNB and LOC. Follow-up ANOVAs and t-tests revealed a consistent pattern of findings across both variables. The data indicated that the reported emotional problems increased with the severity of both LOC and HRNB, except in the most severe groups. The severe subjects when defined by either variable displayed high levels of denial and a lack of awareness of their problems. LOC and HRNB contributed independently to the degree of personality problems, however, LOC was found to be a stronger predictor of personality change than was HRNB at milder levels of severity. The implications of these findings for both treatment and understanding of the mechanisms of head injury are discussed.