  We review the search for the quark-gluon plasma using the signal of the
suppression of J/psi production in high-energy heavy-ion collisions. Recent
observations of anomalous J/psi suppression in high-energy Pb-Pb collisions
observed by the NA50 Collaboration are examined and compared with earlier
results from pA and nucleus-nucleus collisions with heavy ions of smaller mass
numbers. The anomalous suppression of J/psi production in Pb-Pb collisions can
be explained as due to the occurrence of a new phase of strong J/psi
absorption, which sets in when the number of nucleon-nucleon collisions at a
spatial point exceeds about 4 and corresponds to a local energy density of
about 3.4 GeV/fm**3.
