The physical processes driving the different manifestations of the phe nomenon of active galactic nuclei have been studied extensively during the last decade. A major obstacle in all attempts to understand the relevant pro cesses has always been the wide range of frequencies over which significant fractions of the total power are emitted. During the last decade, orbiting telescopes and instrumental improvements for ground-based instrumenta tion provided the means for major advancements on the observational side. The organizers felt that it was timely to organize a meeting to discuss the...

The enormous amounts of energy radiated from the active nuclei of galaxies vary on short time scales, and the emission regions are difficult to observe. To provide a complete understanding of these phenomena a wide variety of studies is presented in this volume. The contributions are broadly divided between line and continuum variability, with observational results, methodological approaches, and theoretical models accompanying each. The final part is devoted to the important aspect of propagation-induced variability.