It is entirely appropriate that a book about unresolved issues in bioequivalence testing starts with a chapter about the Approved Drug Products with Therapeutic Equivalence Evaluations (the Orange Book) (1). Since 1979, the U.S. Food and Drug Administration (FDA) has used the Orange Book to communicate its official position on which drug products are bioequivalent and which products are not. In keeping with the focus of this volume, this chapter will emphasize those aspects of the Orange Book that are most relevant to bioequivalence. The Orange Book also contains a great deal of other valuable information, which will be discussed briefly later in the chapter.