This paper discusses the role of in vitro toxicology in hazard and risk assessment. A short historical overview of the development of the field of in vitro toxicology is given, showing the possibilities, as well as the limitation for using in vitro methods in screening and in studying mechanisms of toxicity. Although the development of the use of in vitro methods over the last two or three decades is vast, the application in risk assessment is still limited. The need for a more integrated approach, i.e. using in vitro data not in isolation, but in combination with data on structure–activity and in silico biokinetic models is discussed. It is foreseen that the role of in vitro methods in future risk assessments will greatly enhance, also in the light of recent developments in technologies such as genomics and systems biology.