The long-term effects of repetitive head trauma on the brain have often been studied in boxers and American football players. The medical literature on this topic was reviewed in order to compare the findings related to boxing with those related to football. The evidence gathered from this review indicates that there are significant differences between the clinical and neuropathological descriptions of the chronic brain damage reported in retired boxers compared to those reported in retired football players. Differing biomechanics of head impacts in the two sports may help explain the different clinical and neuropathological consequences of participation in boxing versus football.