The relationship between brief loss of consciousness, subsequent cognitive and emotional complaints, and impact on daily functioning continues to be hotly debated. The weight of current evidence suggests that uncomplicated minor head injury can cause acute cognitive impairment that is organic in aetiology, but late onset or persisting symptoms result from a psychological response. Traditionally, loss of consciousness has been a prerequisite for the definition of minor head injury but this has been challenged in recent years, although evidence does no more than draw attention to this question. Evidence to support the view that post-traumatic stress disorder can develop after head injury continues to grow. Outcomes in unselected mild head injury patients who attend hospital are not improved by provision of early follow-up.