The subjective and objective sequelae accompanying mild head injury (MHI) are discussed in an attempt to clarify MHI's immediate and long-term consequences. Areas covered included epidemiology, classification, the post-concussive syndrome (PCS), malingering, extent of recovery, rehabilitation and guidelines for clinical practice. Special emphasis is placed on the poor relationship between subjective complaint and objective measures of impairment. Also discussed are some of the methodological problems in the MHI literature, including attempts to match MHI subjects and controls with respect to cognitive and emotional complaint and the possible confounding effects of practice. The evidence for long-lasting (i.e. more than 1 year), subtle neurobehavioral impairment after MHI indicates that additional research is required on MHI 1 year or more after injury.