The nutritional considerations of the ultraendurance athlete center around proper caloric and nutrient intake during training as well as adequate energy and fluid replacement during competition to maintain optimal performance. Energy needs of ultraendurance athletes during training vary widely, depending upon duration, intensity, and type of exercise training. These athletes may train several hours daily, thus risking inadequate caloric intake that can lead to chronic fatigue, weight loss, and impaired physical performance. It is not known whether protein needs are increased in ultraendurance athletes as a result of extended exercise training. Additionally, micronutrient needs may be altered for these athletes while dietary intake is generally over the RDA because of high caloric intake. Prior to competition, ultraendurance athletes should consider glycogen supercompensation and a prerace meal eaten 4 hrs before as a means of improving performance. Carbohydrate feedings during prolonged exercise can significantly affect performance. During events lasting over several hours, sodium sweat losses and/or the consumption of sodium-free fluids may precipitate hyponatremia.