  Recent developments in the theoretical evaluation of charmonium production in
ultrarelativistic heavy-ion collisions (URHIC's) are discussed. In particular,
the consequences of equilibrium properties of open and hidden charm states --
accessible, {\it e.g.}, in QCD lattice gauge calculations -- are assessed.
These include abundances as well as formation and dissociation rates of
charmonia in both hadronic and quark-gluon matter.
