  In statistical QCD, color deconfinement and the properties of the quark-gluon
plasma determine the in-medium behavior of heavy quark bound states. In high
energy nuclear collisions, charmonia probe the partonic medium produced in the
early stages of the interaction. We survey the present theoretical status and
provide a critical evaluation of the charmonium production measurements in
experiments at the CERN-SPS and the BNL-RHIC.
