Adrenal cortical extract (ACE) products were once recommended in the treatment of Addison's disease and for several other indications including hypoglycemia. In January 1978, the Food and Drug Administration (FDA) advised drug firms marketing ACE products that the drug represented a substantial risk of undertreatment because of its low potency and the resulting potential hazard to patients. A review of current well-known textbooks on medicine and endocrinology showed a unanimous preference for using synthetic compounds in the treatment of both the chronic and acute phases of Addison's disease. GAO could not find any medical support for using ACE products in the treatment of hypoglycemia. The regulatory actions taken by FDA against ACE were within its legal authority under the Food, Drug, and Cosmetic Act and were not unreasonable. The use of alternative procedures would have afforded all interested parties a better opportunity to comment on FDA findings and proposed actions; however, the affected drug firms had an opportunity to challenge FDA findings and did not.