Biosimilars (or follow-on biologics) are a new class of medicine, which enters the market subsequent to a previously approved version with demonstrated similarity to innovator biologic products in terms of quality, safety, and efficacy. The European Medicines Agency (EMA) has taken the lead in the regulatory approval framework for biosimilar products, and the World Health Organization (WHO) has published guidelines on the evaluation of biosimilars in order to facilitate the global harmonization. Based on EMA and WHO’s guidelines, many other countries such as Canada, Japan and Korea have also issued their own guidance for evaluating follow-on biologics. The US Food and Drug Administration (FDA) was authorized to approve follow-on biologics by the Biologics Price Competition and Innovation (BPCI) Act passed by the US Congress in 2009, and has circulated three draft guidances in early 2012. The basic concepts and main principles of approving biosimilars are similar among various nations, notwithstanding some differences in regard to the scope, the choice of reference product, and the data requirement. This presentation reviews the regulatory approval pathway of biosimilar products in different regions and current scientific/statistical issues in the United States.