Daily activities and food consumption, for the 2 days before and the day of competition, were investigated in 18 Japanese male triathletes participating in the Ironman Japan Competition at Lake-Biwa in 1991. Energy intakes and the energy intake to expenditure ratio, one and two days before and on race day, were 4005±895 kcal and 151±40%, 5000±1356 kcal and 203±53% and 5170±1799 kcal and 55±27%, respectively. Carbohydrates constituted 62, 4±11.6%, 61.3±7.7% and 76.7±5.6%, respectively, of these meals. Mean vitamin and mineral intakes were highly variable. Total water intake at breakfast and during the events was 7488±3653 ml. Salt intake appeared to be inadequate. Some triathlestes, who consumed only meals (no supplements) or had not stored adequate nutrients prior to the competition, had transiently subnormal nutrient levels during these extremely demanding events.