The incidence of post-traumatic headache varies widely in different series. This paper presents a group of 84 patients aged between 11 and 38 years who had had severe head injuries. All had been unconscious for at least 24 hours and the majority (85%) for over a week. Only 12% had headaches. The incidence of headaches was lower in the more severely injured of the patients as judged by the extent of the physical disabilities and length of unconsciousness, though it was higher in those with severe mental changes. The reasons for the low incidence of headaches in this series are discussed.