A comprehensive summary of progress made during the past decade on the theory of black holes and relativistic stars, this collection includes discussion of structure and oscillations of relativistic stars, the use of gravitational radiation detectors, observational evidence for black holes, cosmic censorship, numerical work related to black hole collisions, the internal structure of black holes, black hole thermodynamics, information loss and other issues related to the quantum properties of black holes, and recent developments in the theory of black holes in the context of string theory. Volume contributors: Valeria Ferrari, John L. Friedman, James B. Hartle, Stephen W. Hawking, Gary T. Horowitz, Werner Israel, Roger Penrose, Martin J. Rees, Rafael D. Sorkin, Saul A. Teukolsky, Kip S. Thorne, and Robert M. Wald.