Participation in ultraendurance events has been increasing. Appropriate nutrition in training and fueling while racing within the confines of gastrointestinal tolerability is essential for optimal performance. Unfortunately, there has been a paucity of studies looking at this special population of athletes. Recent field studies have helped to clarify appropriate fluid intake and dispel the myth that moderate dehydration while racing is detrimental. Additional current nutrition research has looked at the role of carbohydrate manipulation during training and its effect on macronutrient metabolism, as well as of the benefits of the coingestion of multiple types of carbohydrates for race fueling. The use of caffeine and sodium ingestion while racing is common with ultraendurance athletes, but more research is needed on their effect on performance. This article will provide the clinician and the athlete with the latest nutritional information for the ultraendurance athlete.