  Two arguments for the quantization of entropy for black holes in generic 2-D
dilaton gravity are summarized. The first argument is based on reduced
quantization of the only physical observables in the theory, namely the black
hole mass and its conjugate momentum, the Killing time separation. The second
one uses the exact physical mass eigenstates for Euclidean black holes found
via Dirac quantization. Both methods give the same spectrum: the black hole
entropy must be quantized $S= 2\pi n/G$.
