Of 145 patients with concussion from minor head injuries admitted to the Royal Victoria Hospital, Belfast, over one year, 49.0 per cent had no symptoms, 38.9 per cent had between 1 and 6 symptoms, and 2.1 per cent had more than 6 symptoms about six weeks after the accident. There was significant correlation between a high symptom-rate at six weeks and positive neurological signs and symptoms at twenty-four hours. Post-concussion symptoms were more frequent in women, in those injured by falls, and in those who blamed their employers or large impersonal organisations for their accidents. The results suggest that both organic and neurotic factors are involved in the pathogenesis of symptoms at six weeks.