Objective.—To evaluate the occurrence of continued intermittent headache and chronic daily headache in patients with head injury and the relationship between severity of the headache problem and intensity of the head injury. Background.—In the majority of patients with posttraumatic headache, the condition is self-limited, but a minority of patients may develop persistent headaches. The features of posttraumatic headache may vary, but the most distressing type is the chronic daily headache. This study evaluates occurrence of chronic daily headache in relation to the intensity of head injury. Methods.—All patients with head injury who were seen by the senior author (J.R.C.) in the Southern Illinois University Medical School (SIUMS) Neurology Clinic between 1980 and 1991 were identified from the SIUMS headache registry. Data on headache status before and after head injury was obtained, and patients with more than one headache per week before head injury were excluded. Each patient's headache status at the time of the clinic visit was classified as chronic daily headache (headache occurring at least 5 of 7 days for 6 months), intermittent migraine, or no headache. Head injury severity was graded by duration of loss of consciousness or amnesia as minimal (less than 5 minutes), mild (5 to 60 minutes), moderate (1 to 24 hours), or severe (more than 24 hours). Results.—There was an inverse relation between extent of head injury and occurrence of chronic daily headache. For minimal head injury (n = 54), 80% had chronic daily headache, and 11% had no headache, while for moderate/severe head injury (n = 23), only 27% had chronic daily headache, and 68% had no headache (P<.001, χ2). Conclusion.—This study suggests that the risk of developing posttraumatic chronic daily headache is greater for less severe head injury compared with moderate/severe head injury. The reason for this relation is unclear.