It has become more evident during the last three years that the study of interstellar matter is paramount to understand the evolution of the universe and its constituents. From observations of the present state of the interstellar medium, in our galaxy, in other galaxies, and between galaxies, it is possible to test theories of: evolution of the universe, formation and evolution of galaxies, formation and evolution of stars and of the evolution of the interstellar medium itself. The amount of information on the interstellar medium that has been gathered during the 1982-1984 period has been very large and the theoretical models that have been ellaborated to explain these observations have been very numerous, these facts show that the subject of our Commission constitutes a very active field of astronomical research.