Bioavailability/bioequivalence (BA/BE) studies are the cornerstone for the regulatory approval of generic drugs that significantly reduce medical treatment expenditure, especially in resource-limited settings. Bioavailability studies are conducted to determine the rate and extent of absorption, metabolism, excretion rate, and terminal elimination half-life. Bioequivalence studies justify the interchangeable application of different brands of the same drug. Different regulatory agencies of pharmaceutical companies such as the United States Food and Drug Administration (US-FDA) and the Central Drugs Standard Control Organization of India have laid down the systematic guidelines for the conduct of BA/BE studies in various regions of the world. The main scope of these regulatory guidelines is to ascertain the safety, efficacy, and quality of generic drugs on par with the innovator’s small molecules. This chapter briefly discusses the various components of BA/BE studies, namely study subjects and conditions, sample size, study designs, bioanalytical procedures, and bioavailability assessment based on the regulatory recommendations across the world.