  We present a few estimates of energy densities reached in heavy-ion
collisions at the CERN SPS. The estimates are based on data and models of
proton-nucleus and nucleus-nucleus interactions. In all of these estimates the
maximum energy density in central Pb+Pb interactions is larger than the
critical energy density of about 0.7 GeV/fm^3 following from lattice gauge
theory computations. In estimates which we consider as realistic the maximum
energy density is about twice the critical value. In this way our analysis
gives some support to claims that deconfined matter has been produced at the
CERN SPS. Any definite statement requires a deeper understanding of formation
times of partons and hadrons in nuclear collisions. We also compare our results
with implicit energy estimates contained in earlier models of anomalous J/psi
suppression in nuclear collisions.
