Many countries have established procedures for the introduction of generic pharmaceutical products. In order to protect consumers, these generic products must be demonstrated to be therapeutically equivalent to a previously approved product, typically an innovator product. The therapeutic equivalence of a generic and an innovator product is most commonly based on the demonstration of bioequivalence, i.e. clinically insignificant differences in the rate and extent of drug absorption usually assessed from pharmacokinetic measurements. This article reviews the bioequivalence requirements for generic products and, in the interest of promoting international harmonisation, highlights those areas where differences exist among countries.