This article provides a selective review of factors that determine or are related to neuropsychological and psychosocial outcomes after head injury. These include preinjury characteristics of the injured person, head injury severity, other systems injury severity, early neuropsychological status, and time from injury to observation. More information has been accumulated about the relationships between these factors and neuropsychological outcomes than between these factors and psychosocial outcomes. Because many factors determine outcome, difficulties in persons with head injury should not be automatically assumed to be brain-injury related. The importance of natural history information for clinical and research purposes is discussed