INTRODUCTION M. Demedts, M. Delcroix, R. Verhaeghe, G.M. Verleden In the last decade there have been important innovations in the diagnostic work-up and treatment of pulmonary vascular pathology, especially pulmonary embolism (PE) and pulmonary arterial hypertension (PAH). In the field of venous thromboembolism, the novelties in imaging techniques attracted much interest, and new evidence-based diagnostic algoritms are being proposed. As far as therapy is concerned, the low molecular weight heparins gained confidence, and prevention and duration of treatment are fields of increased interest. Finally, the knowledge on genetic and acquired risk factors increased considerably. For pulmonary hypertension, a new World Health Organization classification has recently been published. The pathogenesis has been better understood and a genetic anomaly has been identified in patients with primary pulmonary hypertension. Considerable improvement in quality of life and survival has been obtained with the successive introduction of prostaglandin I2 derivatives and anti-endothelins. Further investigations are underway exploring totally new therapeutical strategies. The purpose of this international symposium on "Pulmonary vascular pathology: a clinical update" organised by the Pulmonary Diseases Department of the University Hospital Gasthuisberg at the Katholieke Universiteit Leuven, Belgium, on March 7–9 2002, was to provide a balanced update of these issues with particular focus on areas that are still investigational. Some 40 clinical and basic researchers and recognised experts in PE or PAH from all over Europe were gathered for 3 days to prepare the present publication. These experts participated in one of two working groups and each group was assigned the task of producing working group reports on risk factors, and diagnostic and therapeutic aspects. In addition, selected reviews were commissioned on several issues, especially related to these topics. It is hoped that this European Respiratory Monograph will provide an interesting synthesis and update of prevention, early detection, diagnostic work-up and manage- ment of PE and PAH. This symposium was accredited as a "European School of Respiratory Medicine" seminar, and was generously sponsored by GlaxoSmithKline, Belgium, in the framework of the "GSK Chair of Respiratory Pharmacology" attributed to G.M. Verleden. We are very grateful to A. Rossi, and E.F.M. Wouters, the past and present editors, respectively, of the European Respiratory Monograph, for granting us the privilege of publishing this symposium as a European Respiratory Monograph. Eur Respir Mon, 2003, 27, b. Printed in UK - all rights reserved. Copyright ERS Journals Ltd 2003 European Respiratory Monograph ISSN 1025-448x. ISBN 1-904097-31-6. b