Bioavailability and Bioequivalence studies play a vital role in drug development process for new drug products and generic drugs. The main aim of abbreviated new drug application is to show that the generic drug is bioequivalent to innovator product in terms of quality, safety, and efficacy. There are several approaches to study bioequivalence and each country has its own regulations for conducting Bioavailability and Bioequivalence studies. The present review gives information about abbreviated new drug application submission and important aspects involved in bioequivalence and Regulatory requirement for various countries.