To avoid adverse effects of hypohydration due to exercise on performance and health, fluid ingestion is recom-mended in accordance to individual, environmental, and exercise characteristics. Attention has been given not only to the timing and the volume of fluid intake but also to the type and the composition of the fluids to be ingested. Research has consistently demonstrated that under conditions of profuse sweating, electrolyte loss, and glycogen depletion, ingestion of solutions containing a proper combination of electrolytes and carbohydrates (CHOs; sports drink) may be advantageous compared with plain water [1–۳]. Ingestion of a sports drink may, therefore, benefit those who practice prolonged exercises, especially in the heat or high-intensity and intermittent frequent efforts. Such drinks (e.g., Gatorade and Powerade) have the purpose of optimizing body hydration, replacing electrolytes (mainly sodium), and maintaining high rates of CHO oxidation as energy supply, which may guarantee perfor-mance. Sports drinks are commercially available in different flavors and colors with bottles ergonomically designed to stimulate voluntary drinking, although excessive fluid ingestion during exercise and hyperhydration are also undesirable. These drinks are commonly used by a wide age range of athletes and active individuals during and after physical activities, being very popular among school-aged children . “Energy drinks” containing other ingredients (caffeine, vitamins, or amino acids such as taurine) have also been commercialized, but so far no convincing evidence exists to support their inclusion during exercise. In fact energy drinks may cause adverse effects in the young popu-lation , and according to a statement from the Committee on Nutrition and the Council on Sports Medicine and Fitness of the American Academy of Pediatrics , they should not be promoted for children, adolescents, and young adults. The purpose of this chapter is to summarize the general impact of hypohydration on a variety of performance scenarios; highlight age-related concerns relative to children, adolescents, and older individuals; and provide practi-cal fluid intake recommendations.