Astrophysics, USA), Dr. G. Trinchieri (Arcetri Observatory, Italy), and Prof. 1. Truemper (MPE, Garching, Germany). The ASI, fully supported by the NATO Scientific Affairs Division, was organized with the intent of providing a critical and up-to-date overview of our present kowledge and understanding of the properties of hot thin plasmas in astrophysics as they are revealed by X-ray observations from space. The X-ray and UV emission from optically thin thermal plasmas is a common feature of many astrophysical systems. This type of emission occurs in the solar corona and in the coronae of other stars, in supernova remnants and in the hot interstellar medium, in normal galaxies and galactic halos, and in the intergalactic gas in clusters.