Soft gamma rays from black holes versus neutron stars.

The recent launches of GRANAT and GRO provide unprecedented opportunities to study compact collapsed objects from their hard X-ray and gamma ray emissions. The spectral range above 100 keV can now be explored with much higher sensitivity and time resolution than before. The author reviews the soft gamma ray spectral data of black holes and neutron stars, radiation and particle energization mechanisms and potentially distinguishing gamma ray signatures. He also outlines some of the highest priority future observations that will shed much light on such systems.