THE ULTIMATE total incidence of epilepsy following craniocerebral injury remains to be determined. It will be partly dependent on the time elapsed since injury and the validity of the methods employed in the detection of posttraumatic epilepsy. The evaluation of such factors as number of patients examined, methods of examination and follow-up observation, definition of the terms "head injury" and "epilepsy," criteria for diagnosis of epilepsy, and recognition and separation of "late epilepsy" and "early epilepsy" has been undertaken previously by me,1 as well as by Denny-Brown,2 Elvidge,3 and Walker.4 The present study deals with the incidence of "late epilepsy," three years after injury to the brain in healthy young men as the result of projectile damage to the scalp, skull, dura, and brain. The material and methods are identical with those employed in my previous examination of incidence two years after injury.1 In addition,