A prospective follow-up study of 60 randomly selected cases of closed adult civilian head injuries was conducted for three months from the time of head injury to assess the frequency, patterns, and factors related to post-traumatic psychiatric disturbances. Eighty per cent of the cases had a neuropsychiatric disturbance as assessed at 1 1/2 months. The commonest was post-concussional syndrome (43 per cent). The extent of social dysfunction was directly related to the severity of head injury. However, the total number of symptoms (largely subjective) correlated highly with pre-traumatic neuroticism. The inter-relatedness of organic and personality factors in the post-traumatic syndrome, and their predictive value, are discussed.