J/psi suppression in ultrarelativistic heavy ion collisions
has been predicted to be a signature of the transition from
normal hadronic matter to a quark-gluon plasma. Several
experiments have been devoted to charmonia production at
the CERN/SPS: NA38, NA50 and NA60. All the results obtained
so far in proton-proton, proton-nucleus and nucleus-nucleus
collisions will be summarized. Particular focus will be
dedicated to the proton-nucleus studies (and comparison to
other experiments) needed to determine the normal nuclear
absorption, which knowledge is essential in order to
extract the anomalous suppression obtained in
nucleus-nucleus collisions.