With the Compton Gamma-Ray Observatory (CGRO) now in its ninth year of operation, the Fifth Compton Symposium provided an opportunity for sharing the most recent scientific results from CGRO and other related experiments in gamma-ray astronomy. Equally important were the descriptions of several new space-based and ground-based experiments in gamma-ray astronomy. These new instruments will be responsible for continuing the pioneering efforts of the CGRO mission. The proceedings provide a valuable reference for researchers in high energy astrophysics.

This volume consists of invited lectures and seminars presented at the NATO Advanced Study Institute "The Gamma Ray Sky with COMPTON GRO and SIGMA" , which was held at the Centre de Physique Theorique of Les Houches (France) in January / February 1994. The school has been planned by a Scientific Organizing Committee. It was organized with the aim of providing students and young researchers with an up-to-date account of the high-energy phenomena in the vicinity of compact objets and the diffuse gamma-ray backgrounds after the early results from the gamma-ray telescope SIGMA and the four instruments onboard COMPTON GRO (Gamma Ray Observatory) : BATSE (Burst and Transient Source Experiment),COMPTEL(Compto'l Telescope),EGRET (Energetic Gamma Ray Experiment Telescope) and OS SE(Oriented Scintillation Spectrometer Experiment) . It was attended by more than sixty researchers from many countries. The lectures and seminars represent a complete coverage of our present knowledge and understanding of: Gamma-ray backgrounds, Gamma-ray Burts,Active Galactic Nuclei,Galactic Compact Objects, Gamma-ray Spectroscopy, Instrumentation and observation techniques, etc ... Most of these lectures are reproduced in this volume. Unfortunately, a few lecturers have chosen not to submit their manuscript.

This volume presents complete results of the discoveries made by the Compton Gamma-Ray Observatory. Papers by Carl Fichtel, Gerald Fishman, James Kurfess, and Volker Schonfelder, principal investigators for the four on-board instruments, highlight this work. It contains coverage of supernovae, galactic sources, solar flares, and pulsars, and is intended for students and researchers in astronomy and astrophysics.