During exercise, especially endurance exercise in the heat, vital body fluids and essential ions are lost in sweat, and the body may deplete its glycogen stores. Unless essential body fluids are restored, these conditions can produce hypovolemia, hypoglycemia, hyponatremia, hyperthermia, and dehydration. Performance may also be reduced. This paper briefly reviews pertinent aspects of gastric emptying and intestinal absorption and proposes the formulation of beverages for ingestion both pre-event and during exercise. For events lasting less than 1 h, 300-500 ml of a 6-10% CHO beverage is recommended pre-event (0-15 min), and cool (5-15 degrees C) water in a volume approximately half the subjects sweat rate is recommended during exercise. For events between 1-3 h long, 300-500 ml of water is recommended pre-event, and 800-1600 ml.h-1 of a 6-8% CHO solution with 10-20 mEq Na+ is recommended during exercise. For events longer than 3 h, 300-500 ml of water is recommended pre-event, and 500-1000 ml.h-1 of a 6-8% CHO beverage with 20-30 mEq Na+ is recommended during exercise. In recovery, a beverage containing 5-10% CHO with 30-40 mEq Na+ should be ingested to achieve euhydration. A minimum of 50 g.h-1 of CHO should be ingested in the first 2 h to maximize glycogen repletion. Guidelines to follow in formulating these beverages are reviewed and the rationale for each formulation is provided.