The legislative history of the United States Orphan Drug Act began with rare, unanimous approval by the United States Congress. The Act, mid consequently the Regulations, have evolved since then. The two-stage process of Orphan Drug designation and approval is outlined, as well as the incentives that are offered to commercial companies for their implementation. Orphan Drugs are likely to be over-represented among drugs used under "Treatment" INDs. For patent- and "drug-difference" reasons, the benefits under the Orphan Drug Act are especially valuable to those who develop biologics. By any measure, this legislation, which requires only voluntary participation, has been a success; because the human genome is likely to lead to more biologicals than orthodox drugs, this success is likely to continue into the future. But even so, the 18-year experience with Orphan Drugs in the United States has led to some 225 Orphan Product approvals that benefit many millions of patients.