Supernova Propagation in the Circumstellar and Interstellar Medium

We describe the propagation of supernova shocks within the surrounding medium, which may be due to mass-loss from the progenitor star. The structure and density profile of the ejected material and surrounding medium are considered. Shock wave interaction with clouds and wind-bubbles, and issues relevant to cosmic rays are briefly discussed.
Comment: 6 pages, 3 figures. Final version, minor changes. Invited review presented at the conference on Cosmic Rays and the Interstellar Medium (CRISM-2011), Montpellier, France, June 26-July 1. Published in a special issue of MEMORIE della Societa Astronomica Italiana