Low residue, chemically defined diets containing all essential nutrients in a readily assimilated form, require minimal digestion and are almost entirely absorbed in the upper gastrointestinal tract. Within the past decade, these diets have been reported to provide nutritional support in a variety of clinical situations. The chemically defined diets presently available commercially differ in several respects. In order to provide optimal nutritional care utilizing chemically defined diets, the physician should compare the diet formulas and make the most appropriate choice for each individual patient. A comparative nutritional analysis of the currently available chemically defined diets is given.