This chapter discusses the data related to fluid and electrolyte deficits during exercise in young female and male athletes and its effects on thermal strain and decrements in endurance performance and sports skills. The benefits of carbohydrate-electrolyte drinks to promote a greater fluid intake and minimize dehydration will be discussed as well as impediments that young athletes face when trying to rehydrate, and ways to facilitate fluid intake before, during, and after exercise. Young athletes participating in these sports show higher sweat rates and dehydration levels during competition than during training, due to the higher intensities of exercise and less focus on hydration. Due to ethical constraints, no studies have specifically examined the core temperature-dehydration relationship in the laboratory or playing field in young athletes in the past 35 years, and there is a gap in our understanding of thermoregulatory strain due to dehydration in young athletes.