The injuries sustained in 6 national karate competitions in Finland were studied by analyzing data from 450 bouts during the season 1991-1992. The analyzed data included a personal interview with each competitor and detailed information on the bouts and any injuries sustained. The overall probability of injury was 0.28 per bout. These injuries occurred to 16% of the 647 competitors. Occurrence of injury was greatest among adult men, which was pronounced in final bouts. Of all injuries diagnosed by the physicians for the competitions, more than 95% were localized to the head. The majority of these were minor injuries. Experienced competitors were more injury-prone than beginners. On the other hand, none of the background factors studied significantly affected the probability of injuring one's opponent. Most injuries and penalties, as well as full scores, were caused by direct punches to the head. From these findings it was concluded that a protective guard for the head together with modification of competition rules could significantly reduce injuries.