Biosimilars, also known as follow-on biologics, continue to be an area of great interest in oncology because of the potential cost savings and improved access related to their use, yet significant confusion remains regarding their introduction in the United States. The regulatory and legal hurdles remain poorly defined, and companies producing branded products have been battling their introduction. The European Union provided a pathway for approval in 2004, with various agents reaching the market since that time. It is important to understand the nuances of the discussion and experiences and for clinicians and policy makers to take an active part in defining the role of biosimilars. Several outstanding questions remain, including the degree to which physiochemical, biologic, quality, and clinical end points must be demonstrated in clinical trials compared with the use of analytic data for approval; whether off-label indications should be embraced; and the regulatory rules around areas such as marketing and interchangeability. This article highlights tbo-filgrastim, an agent currently marketed as a biosimilar in Europe, because its pending introduction in the US market provides insights into the potential of these agents.