The symbiosis between particles physics and cosmology has virtually become a conjugal relationship. Hence the 9th biennial Course of the International School of Cosmic-Ray Astrophysics was designed to bridge these formerly disparate disciplines. This NATO Advanced Study Institute took place at the Ettore Majorana Centre in Erice, Italy, June 20-30, 1992. Seventy participants from 17 countries participated in lively interactions and enjoyed the stimulating lectures that form the basis for this volume. The book includes current advances in both astrophysics (cosmic gamma rays, X-rays, cosmic rays) and cosmology (an introduction to inflation in big-bang theory, the age of the universe, nucleosynthesis in the early universe). It is suitable for reading and study by all interested physical scientists, especially those having a limited specialized background in astrophysics and cosmology.