A sufficient variety of semisynthetic dietary products is now available to permit control of amino acid imbalance in several inborn errors of metabolism. However, they must be used carefully, and their effects monitored closely. Continuing development of products for this type of special diet—to provide a wider variety—is necessary. Regionalization of treatment programs for patients with inborn errors of metabolism is recommended. Metabolic centers which are accumulating experience and have good laboratory support may be the most efficient way of providing adequate treatment for patients with inborn errors of metabolism.