  The centrality dependence of the charged-particle multiplicity density at
mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV is
presented. The charged-particle density normalized per participating nucleon
pair increases by about a factor 2 from peripheral (70-80%) to central (0-5%)
collisions. The centrality dependence is found to be similar to that observed
at lower collision energies. The data are compared with models based on
different mechanisms for particle production in nuclear collisions.
