  We study the production of $c \bar{c}$ pairs and dimuons from hard collisions
in nuclear reactions within the covariant transport approach HSD, which
describes successfully both hadronic and electromagnetic observables from p+A
and A+A collisions from SIS to SPS energies. The production of $c \bar{c}$ and
Drell-Yan pairs is treated perturbatively employing experimental cross sections
while the interactions of $c\bar{c}$ pairs with hadrons are included by
conventional cascade-type two-body collisions. Adopting 6mb for the $c
\bar{c}$-baryon cross sections the data on $J/\Psi$ suppression in p+A
reactions are reproduced in line with calculations based on the Glauber model.
We study different models for $c \bar{c}$ dissociation on mesons in comparison
with the experimental data of the HELIOS-3, NA38 and NA50 collaborations.
Adopting absorption cross sections with mesons above the $D\bar{D}$ threshold
in the order of 1.5 - 3mb we find that all data on $J/\Psi$ suppression from
both proton-nucleus and nucleus-nucleus collisions can be described without
assuming the formation of a quark-gluon plasma in these collisions.
