This volume, together with those on Cosmic Rays in the Heliosphere and on Cosmic Rays at Earth, rounds off a trilogy devoted to cosmic rays. It specifically deals with the astrophysical sources and acceleration processes of cosmic rays. The principal aims are to examine the cosmic ray phenomenon in the context of our evolving understanding of the Galaxy as an astrophysical system. Observations of cosmic rays, and theoretical models of their origin and propagation, are critically reviewed. The extent to which these reinforce, or conflict with, other astronomical information about the Galaxy is addressed. Other themes are the extent to which galactic-scale processes can be illuminated by studies or analogous heliospheric processes, and the identification of key questions for future investigations.