  The production of charmonia is investigated for heavy-ion collisions from SPS
to RHIC energies. Our approach incorporates two sources of $J/\Psi$ yield: (i)
a direct contribution arising from early (hard) parton-parton collisions,
subject to subsequent nuclear absorption, quark-gluon plasma and hadronic
dissociation, and (ii) statistical production at the hadronization transition
by coalescence of $c$ and $\bar{c}$ quarks. Within an expanding thermal
fireball framework, the model reproduces $J/\Psi$ centrality dependencies
observed at the SPS in Pb-Pb and S-U collisions reasonably well. The study of
the $\Psi'/\Psi$ ratio at SPS points at the importance of the hadronic phase
for $\Psi'$ interactions, possibly related to effects of chiral symmetry
restoration. Predictions are given for the centrality dependence of the
$N_{J/\Psi}/N_{c\bar{c}}$ ratio at full RHIC energy. We also calculate the
excitation function of this ratio. The latter exhibits a characteristic minimum
structure signalling the transition from the standard $J/\Psi$ suppression
scenario prevailing at SPS to dominantly thermal regeneration at collider
energies.
