  We derive a simple analytical scaling function which embodies the predictions
of high density QCD on the energy, centrality, rapidity, and atomic number
dependences of hadron multiplicities in nuclear collisions. Both centrality and
rapidity dependences of hadron multiplicity in $Au-Au$ collisions as measured
at RHIC at $\sqrt{s}= 130 {GeV}$ are well described in this approach. The
centrality and rapidity dependences of hadron multiplicity at $\sqrt{s}= 200 \
{GeV}$ run at RHIC are predicted; the variation of these dependences with
energy appear different from other approaches, and can be used as an important
test of the ideas based on parton saturation and classical Chromo-Dynamics.
