  We have considered the divergence structure in the brick-wall model for the
statistical mechanical entropy of a quantum field in thermal equilibrium with a
black hole which {\it rotates}. Especially, the contribution to entropy from
superradiant modes is carefully incorporated, leading to a result for this
contribution which corrects some previous errors in the literature. It turns
out that the previous errors were due to an incorrect quantization of the
superradiant modes. Some of main results for the case of rotating BTZ black
holes are that the entropy contribution from superradiant modes is positive
rather than negative and also has a leading order divergence as that from
nonsuperradiant modes. The total entropy, however, can still be identified with
the Bekenstein-Hawking entropy of the rotating black hole by introducing a
universal brick-wall cutoff. Our correct treatment of superradiant modes in the
``angular-momentum modified canonical ensemble'' also removes unnecessary
introductions of regulating cutoff numbers as well as ill-defined expressions
in the literature.
