This volume contains all but one of the lectures and seminars presented at the NATO Advanced Study Institute on HOI Thin Plasmas in Astrophysics held in Cargese, Corsica, from September 8 to 18, 1987. The meeting was planned in collaboration with the members of the Scientific Organizing Committee, 10 whom I am grateful for suggesting a comprehensive and well balanced program. The SOC was comprised of Prof. J. Bleeker (Space Research Institute. Utrecht, The Netherlands), Dr. C. Cesarsky (CEN Saclay, France), Dr. R. Mushotzky (GSFC, USA), Prof. K. Pounds (University of Leicester, UK), Prof. H....