There is insufficient information about the long-term sequelae of mild head injury (postconcussional symptoms, PCS). Therefore, a questionnaire-based investigation was carried out in patients 1-5 years after mild head injury (MHI) and in non-concussed subjects in order to study the nature of long-term complaints after MHI. A three-factor model of residual subjective and psychological complaints that contained a dysthymic factor, a vegetative/bodily complaints factor, and a cognitive performance factor were identified in the patient population. Three rating scales were constructed from the relevant items or factors, and were used to compare the MHI patients with non-concussed controls. It was found that the profile of distresses and discomforts mentioned by a population of MHI patients 1-5 years after the trauma was similar to that of a non-concussed control population. These symptoms were indistinguishable from those encountered in ordinary everyday life. These symptoms were significantly more severe in the MHI patients. Stepwise regression analysis in the patient population indicated that a number of parameters were statistically of predictive importance: comorbidity, sex, and neurological complication at the time of the trauma. The results support the hypothesis that MHI may not ever be completely reversible.