The objective of this meeting was to bring together collea gues from different branches of observational astronomy and theoretical astrophysics to discuss and analyse the rapid progress in our knowledge and understanding of the matter surrounding stars, streaming off stellar surfaces, or fall ing onto stars. The meeting was sponsored by IAU Commis sions 36 (Theory of Stellar Atmospheres), 29 (Stellar Spec tra), and 34 (Interstellar Matter). There were two special reasons for organizing this meeting at Heidelberg in 1986: During this year the University of Heidelberg celebrated its 600th...