Supernova explosions are not only important to the ecology of the universe, seeding it, among other things, with the heavy elements necessary for the existence of life, but they are also a natural laboratory in which a host of unique physical phenomena occur. While still far from a complete understanding, scientists have made great advances during the last twenty-five years in understanding the nature and conse- quences of supernovae. This book presents the state of supernova studies at the beginning of the 1990's, as reported at a two-week meeting on the Santa Cruz campus of the University of California in July 1989 in- volving 177 astronomers and astrophysicists from 17 nations. The 110 papers contained in this volume report all aspects of the field - observations at all wavelengths from radio through gamma-rays, bolometric light curves and spectra, neutrino observations, the theory of stellar explosions, multidimensional models for mixing, nucleosynthesis calculations, synthetic spectral modeling, presupernova evolution, supernova remnants, supernova rates, supernovae as standard candles, the interaction of supernovae with their surroundings - and constitute the most comprehensive and up-to-date treatment of SN 1987A currently available. Astronomers and astronomy graduate students will find this an in valuable summary of the current state of supernova research. The informed layperson or undergraduate astronomy student will also find it a useful introduction and guide to the literature in the subject.