Krolik, Julian 96-16922 Dr. Krolik will study the possible structures of accretion onto massive black holes. Current views cover the range from a thin, cool, very dense disk to a quasi-spherical two temperature plasma. The goal of this study is to evaluate the plausibility of the current models and perhaps find additional ones. Also included will be the calculation of new predictions made by the various candidate models, so that further observational tests may be applied to them.