For selected patients, especially those with hepatic or renal failure, it may be necessary to restrict fluid, protein, electrolytes, and/or other micronutrients. The provision of enteral formulas with fixed percentages of nutrients that need to be restricted often results in the patient's receiving inadequate amounts of many that do not need to be restricted. One means of avoiding this problem is to use a micronutrient-free commercial solution, thus allowing the controlled addition of specific micronutrient "modules" needed to meet nutritional goals. There are only two formulas of this type available; however, they are more costly than any other product in our formulary and contain specific amino acid patterns developed for a specific disorder. We have designed, from macronutrient and micronutrient modules, modular tube feeding diets that can vary according to patient needs. We report on five patients treated. The protein quality (chemical score) provided by the modular diet is better than that provided by the nonmodular diet. The average daily cost to the hospital for a modular diet, including labor, is approximately one-third the cost of the nonmodular commercial diet, including labor ($7.72 vs $28.93). One anticipated difficulty is the high level of nutrition knowledge required by the prescribing individual.