Particle astronomy - the study of cosmic radiation - was the first of the new astronomies to emerge in the twentieth cen­ tury. Although cosmic-ray phenomena have been fruitfully investi­ gated for some seventy years, the central engima - the origin of these high-energy particles - remains a challenge. Among the ob­ servational clues to possible sites and mechanisms of cosmic-ray production, none carries more information than the composition and energy distribution of the particles arriving in the solar system. The present volume is the work of many participants in a NATO Advanced Study Institute on "The Composition and Origin of Cosmic Rays" held from the 20th to the 30th of June, 1982 under the aus­ pices of the Ettore Majorana Centre for Scientific Culture. Par­ ticipants came to the Centre in Erice, Sicily from eight countries. This Institute was also the third Course of the International School of Cosmic-Ray Astrophysics, which has been meeting bienni­ ally 1n Erice. Of the two previous Courses, likewise sponsored by the Majorana Centre, the first (1978) provided a broad introduction to th~ field. It was entitled "Progress and Problems in Cosmic­ Ray Physics." The second (1980) was devoted to "Acceleration of Particles in Nature." It treated mechanisms of acceleration, some candidate sites, and observational and theoretical constraints. Director of the Majorana Centre is Prof. Antonino Zichichi.