Traditionally, In-Use Compliance testing is closely related to homologation legislation, as in most cases the IUC test is a derivative from the type approval test. As it is the aim of this paper to explore the future of IUC testing, this can be studied best on the basis of expectations for future homologation test procedures that also include vehicles with advanced powertrains. Within the framework of an European project, research has been carried out by TNO Automotive and other research institutes, aimed at the development of adequate measurement methods and test procedures for the evaluation of energy use and emissions of such vehicles. A number of the identified problems that may occur when vehicles with advanced powertrains are tested by current homologation procedures, are discussed in this paper to indicate the nature, size and impact they have on these procedures. Though absolute solutions for these problems are not available at this moment yet, it is already possible to sketch the consequences they will bring for future homologation legislation. Based on these findings, an outlook to the future of IUC testing is drawn. One of the major conclusions concerns the fact that it is an absolute requirement for test cycles to become representative for real-life conditions, a quality that is absent in most current test cycles. TNO Automotive has gained a lot of experience in this field. Therefore, special attention is given here to their view of how representativity can be ensured best in a test cycle.