Health Affairs — Widespread adoption of generic medications, made possible by the Hatch-Waxman Act of 1984, has contained the cost of small-molecule drugs in the United States. Biologics, however, have yet to face competition from follow-on products and represent the fastest-growing sector of the US pharmaceutical market. We compare the legislative framework governing small-molecule generics to that which regulates follow-on biologics, and we examine management tools that are likely to be most successful in promoting biosimilars’ adoption.