To study the efficacy of an injury prevention program in a randomized trial, 12 teams (180 players) in a male senior soccer division were followed up for 6 months. The 12 teams were allocated at random to two groups of six teams, one being given a prophylactic program and the other serving as control. The program was based on previous studies of injury mechanisms. It comprised (1) correction of training, (2) provision of optimum equipment; (3) prophylactic ankle taping; (4) controlled rehabilitation; (5) exclusion of players with grave knee instability; (6) information about the importance of disciplined play and the increased risk of injury at training camps; and (7) correction and supervision by doctor(s) and physiotherapist(s). The injuries in the test teams were 75% fewer than in the controls. The most common types of soccer injuries, sprains and strains to ankles and knees, were all significantly reduced. It is concluded that the proposed prophylactic program, including close supervision and correction by doctors and physiotherapists, significantly reduces soccer injuries.