Dilepton signals in heavy ion collisions at the CERN SPS

This paper overviews the main results on dilepton and heavy flavour production in heavy ion collisions, obtained in measurements done at the CERN SPS, over the last few years. The presently available results are very interesting, indicating the production of a new state of matter in central Pb-Pb collisions at SPS energies. However, important questions remain open. New and improved measurements are needed to confirm beyond reasonable doubt the formation of a deconfined state of matter in heavy ion collisions at the SPS. The future data of a recently proposed experiment, to be carried out in the SPS in the years 2001-2003, should provide a much deeper understanding of the "new state of matter" hypothetically found at CERN. (26 refs).