Despite recent attempts to define acute injury characteristics of mild traumatic brain injury (MTBI), neuropsychological outcome is often unpredictable. One hundred MTBI cases were prospectively collected, which were consecutive referrals to a concussion clinic, and the roles of various acute neurologic variables were examined in relation to neuropsychological status and vocational outcome. Significant differences were found between subgroups of patients classified by (1) mechanism of injury (i.e. acceleration/deceleration trauma in which the head strikes an object (HSO) versus acceleration/deceleration trauma in which the head does not strike an object (HNSO) versus trauma in which an object strikes the head (OSH), and (2) type of injury (i.e. motor vehicle collision, fall, assault, motor vehicle-pedestrian collision, falling object, sports/recreation). There was no difference, with respect to neuropsychological status or vocational outcome, between patients who had positive findings on computerized tomography (CT) versus those who were CT negative. Additionally, there was no difference between patients who had suffered brief loss of consciousness (LOC) and those without LOC. These findings suggest that selective acute injury characteristics may be used to classify subtypes of MTBI patients.