INTRODUCTION W. Timens*, H.H. Popper # *Dept of Pathology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands. Fax: 31 503632510 E-mail: w.timens@path.azg.nl # Dept of Pathology, Laboratories for Molecular Cytogenetics, Environmental and Respiratory Pathology, Medical University of Graz, Austria. Fax: 43 31638583646 E-mail: Helmut.popper@meduni-graz.at Pathology is a discipline that, in interaction with clinicians active in pulmonary medicine, plays an important role in the diagnosis and, in recent years, also in the evaluation of therapy. No less important, the core research in pathology has always been aimed at understanding disease mechanisms. With respect to understanding and diagnosing diseases of the lung, an important challenge and difficulty is that this unique organ has an open connection with the outside world. This results in a large variation in disease presentation, with a mix of hallmarks of underlying disease with environmental effects, such as from smoke, pollution or occupational exposures. With respect to pulmonary diseases with the resulting complex presentation, pathology has its own role, which, in a multidisciplinary approach, can contribute to a better understanding of pathogenesis. The present Monograph is aimed at clinicians active in pulmonary medicine and at pathologists with an active interest in pulmonary pathology. This Monograph does not cover a truly thematic subject, but rather new trends and advances in a discipline with an active interaction with pulmonary medicine. The Guest Editors have chosen different areas of pulmonary pathology to focus on and have asked experts within those fields to contribute, adding to new views and perspectives. Therefore, several chapters have been co-written by a pathologist and a physician. It was the Guest Editors’ aim to obtain an interesting blend of state-of-the-art work, which is relevant for both pulmonary physicians and pathologists based in daily clinical work, as well as colleagues with an interest in recent research advances in pulmonology. As this Monograph exemplifies the long-standing fruitful collaboration between pathology and different areas of pulmonary medicine, it is hoped that it may also serve in sustaining this interaction and collaboration. Eur Respir Mon, 2007, 39, viii. Printed in UK - all rights reserved. Copyright ERS Journals Ltd 2007 European Respiratory Monograph ISSN 1025-448x. viii