Traumatic brain injury (TBI) refers to a broad range of neurological, cognitive and emotional factors that result from the application of a mechanical force to the head. Mechanical force can be applied on a continuum from none to very severe, and the extent of brain injury is related to the severity of this force. A review of the literature reveals that, while considerable research has been done on minor head injury, there remain several major sources of confusion. First, one of the most noticeable problems relates to the fact that the mild head injury has lower limits which are vaguely defined. This leads to individuals being categorized as having sustained a mild TBI despite minimal or no neurological damage being present. A second source of confusion in the literature is related to the failure to differentiate between cognitive consequences of TBI and post-concussion symptoms (PCS). Since PCS can occur in the absence of head injury, and are often present beyond the period of cognitive recovery from mild TBI, the two clearly result from different factors. Researchers have often failed to separate these two factors when studying recovery of function, and this has led to varying findings on outcome. Finally, many pre-injury factors (age, education, emotional adjustment) and post-injury factors (pain, family support, stress) interact with cognitive functioning and significantly affect recovery from TBI. These problems are reviewed and discussed.