ABSTRACT:Pharmaceutical Regulatory Affairs (PRA) is a vital unit in a pharmaceutical company that successfully drives the Research and Development (R&D) efforts of the company to the market. In the present scenario, countries have different regulatory requirements for approval of a new drug. The single regulatory approach for marketing authorization application (MAA) of a new drug product applicable to various countries (on the basis of single dossier) is utmost difficult. Therefore, the knowledge of exact and detailed regulatory requirements for MAA of each country should be known to establish a suitable regulatory strategy. CTD was developed with the aim to provide a common format for the technical documentation that would significantly reduce the time and resources needed to compile applications for registration of human pharmaceuticals and would ease the preparation of electronic submissions. Bioavailability and bioequivalence testing are essential in the drug development process as they create the foundation for regulatory decision making when evaluating formulation changes and lot-to-lot consistency in innovator products. They also serve as the primary components to demonstrate therapeutic equivalence between generic products and the reference innovator product. This article will focus the similarities and differences in drug approval process & requirements of the documents/CTD specifications to the drug regulatory authorities in the Europe, USA and India also focuses on submission and work flow related to bioavailability and bioequivalence studies.