The research literature indicates that the great majority of persons who sustain any initial neuropsychological impairment from a mild head injury recover in 1 to 3 months. Nevertheless, clinicians report that some persons with a mild head injury demonstrate signs and report symptoms suggesting that they have sustained permanent brain damage. Although this latter group contains the participants of principal clinical interest, our literature review did not identify any research that provided a comprehensive description of the neuropsychological characteristics of this important subgroup of mild head-injured persons. The present investigation compared four groups: (1) controls, (2) persons with definite traumatic brain tissue damage, (3) persons with mild head injuries routinely accessed into a research study, and (4) persons with mild head injuries who had persisting clinical signs and symptoms. The same comprehensive neuropsychological test battery was used to evaluate all four groups. All pairs of groups differed significantly in neuropsychological status, with Group 3 showing only mild impairment (approaching the level of the controls) and Group 4 showing significant impairment (approaching the level of the group with definite brain tissue damage). The results emphasize the need for a comprehensive neuropsychological examination of persons with mild head injuries who have persisting clinical problems.