JET is the machine whose parameters are the closest to those of ITER and at present the only one that can use tritium and beryllium. JET can make essential contributions to ITER with regard to qualifying ITER scenarios at low normalized Larmor radius, consolidating the ITER design choice for plasma-facing components and heating systems, developing control tools and techniques, and providing a basic understanding of plasma dynamics. Consequently, an enhancement program has been launched that will be completed in 2010. A deuterium-tritium experiment should be envisaged, after testing of the ITER-like wall, to allow extrapolation of the scenarios to ITER-relevant conditions. JET will be the ideal machine where the collaboration among the scientists of the various ITER parties could be started in advance of ITER operations.