We study anti-de Sitter black holes in 2 +/- 1 dimensions in terms of Chern
-Simons gauge theory of the anti-de Sitter group coupled to a source. Takin
g the source to be an anti-de Sitter state specified by its Casimir invaria
nts, we show how all the relevant features of the black hole are accounted
for. The requirement that the source be a unitary representation leads to a
discrete tower of excited states which provide a microscopic model for the
black hole.