Abstract
An enhanced production of dileptons - e(+)e(-) or mu(+)mu(-) known hadronic sources, has been observed in S-induced interactions on heavy targets at 200 GeV/nucleon, by the three experiments - CERES, HELIOS-3 and NA38 -, dedicated to the measurement of dileptons at the CERN SPS. The excess covers a very broad invariant mass-range from 200 MeV/c(2) up to the J/psi. On the other hand there is no clear evidence of a signal in the search for direct photons carried out by the CERES and the WA80 experiments. The properties of the low-mass dilepton excess suggest that it originates from two-pion annihilation pi(+)pi(-)-->l(+)l(-). Possible interpretations invoking a phase transition into the quark-gluon plasma or using decreasing rho and omega meson masses in hot and dense hadronic matter are discussed.