The Austrian Pneumological Society held its 33th Workshop on "Clinical Respiratory Physiology" at Graz, November 1st - 3rd, 1990. Sleep related breathing disorders have been known for many years to be an important cause of daytime disability I a huge amount of literature about this topic has been written in the last ten or fifteen years. Because of the practical relevance owing to the high competence of the authors we hope that the lectures and discussions we had at Graz will enjoy and inform the interested reader. I want to express my deep gratitude to all the authors for providing us with the manuscripts and graphs. I am especially grateful to Mrs. H. Weber for her secreterial work and to Mrs. Mag. A. Lahrmann-Ramharter for correcting the written version of the speeches and preparing a manuscript that was ready for the press. Prim. Dr. Hartmut Zwick Contents Douglas J. N.: Breathing During Sleep................... 1 Krieger J.: Pulmonary Hemodynamics in Sleep Apnea .................................16 Peter J. H.: Epidemiology of Sleep Related Breathing Disorders with Obstruction of the Upper Airways.....................