With the increasing participation in triathlons of all distances has come a corresponding increase in the need for competent medical information relating to the care of these triathletes. Although medical organization at triathlons involves certain principles which should be applied regardless of race specifics, there are certain other arrangements that will vary with the size and length of the event. For example, the longer races require a reliable communication system, fully equipped mobile response teams, and a larger number of medical staff. Medical communication needs can be served by having priority medical transmissions via UHF radio from mobile vans to a main medical station. An average of 2.5 physicians and 7.5 nurses and other paramedical volunteers for each group of 100 competitors has been found to be sufficient to meet the medical needs of triathletes. The swim, although having the greatest potential for catastrophe, accounts for only 1-3% of medical visits at the Hawaii Ironman Triathlon. Ten percent of injuries requiring medical evaluation at the Hawaii Ironman occur during the bike portion of the race. The rest occur either during the run or after finishing. Seventy-one percent of the total medical visits come directly from the finish line. Dehydration and exhaustion account for the majority of primary medical diagnoses. Appropriate medical care at triathlon races is necessary to aid athletes in safely experiencing their physical potentials.