Criteria for assessment of bioequivalence for generic drug products are reviewed. These criteria include criterion for average bioequivalence, criteria for population and individual bioequivalence, and a recent proposed scaled average bioequivalence (SABE) criterion for highly variable drug products. In addition, following similar idea of IBE and the development of SABE, a new criterion for assessment of drug interchangeability is proposed. A numerical study was conducted to illustrate the use of the proposed criterion. In addition to the assessment of drug interchangeability for generic drug products, the proposed criterion can be applied to the assessment of drug interchangeability for biosimilar products.