The imminent expiry of patents on biological medicinal products, such as epoetin alfa in 2006, has significant implications for nephrology in Australia. The purpose of this review is to examine the differences between biosimilars (similar biological medicinal products) and generic low molecular weight (chemical) drugs. The approach that regulatory agencies, including the European Medicines Agency (EMEA) and the Therapeutic Goods Administration (TGA), are taking towards biosimilars is also discussed. Biosimilars differ from generic chemical drugs in many important ways, including the size and complexity of the active substance, the nature of the starting materials (cell banks, tissues and other biological products), and the complexity of the manufacturing processes. Therefore, it has been acknowledged by the EMEA that established legal and regulatory principles of 'essential similarity' that are applied to standard chemical generics cannot be readily applied to biosimilars. One of the key areas of concern with the introduction of biosimilars into the field of nephrology will be guaranteeing the safety and efficacy of biosimilars. New manufacturers will need to ensure that their biopharmaceutical has a similar efficacy and safety profile to the innovator product through more extensive clinical trials than the limited testing done for generic versions of low molecular weight chemical medicines.