Production and Suppression of Charmonium in Nuclear Collisions

$J/\psi$ production cross section considering the contributions of both color-singlet and color-octet $c\bar c$ channels is calculated. The result is used to study the suppression of $J/\psi$ in nuclear collisions. With absorption cross sections for $(c \bar c)_8$ $\sigma_{abs}^8\simeq 11mb$ and $(c \bar c)_1$ $\sigma_{abs}^1\simeq 0mb$ the p-A and A-B data except for Pb-Pb can be explained. Possible explanations of additional suppression in Pb-Pb are discussed.