PREFACE Preface Present day insights into the relationship between gender and health emphasise the necessity of taking sex and gender differences into consideration. Sex refers to biological characteristics such as chromosomes, physiology and anatomy that distinguish females and males. Gender refers to the array of socially constructed roles and relationships, personality traits, attitudes, behaviours and values that society ascribes to the two sexes on a differential basis. Sex is considered a quality and gender a process with effects on the personal, societal and symbolic level. The Philosophical introduction by M. Leo in this issue of the Monograph further elaborates this gender concept. In health-related research both sex differences and differences resulting from gender are implied. Sex can determine differential propensities for certain health conditions or diseases, different risk factors or treatment requirements. These sex differences have, for a long time, only been recognised in the domain of reproductive health but clearly transcend reproductive systems. Sex differences must therefore be taken into account in research protocols, methodologies and analysis of results especially in the field of genomics. Gender can determine different exposures to certain risks, different treatment seeking patterns or differential impacts of social and economic determinants. However, gender influences are largely related to the dynamic and changeable nature of the social and cultural systems. The combined effects of sex and gender affect health status, health system responses and health outcomes and lack of attention to these differences in research can contribute to problems of validity, generalisation as well as inappropriate healthcare for women. The present issue of the Monograph, edited by S. Buist and C.E. Mapp, offers an excellent overview of the present knowledge about sex and gender differences in the different domains of respiratory medicine and aims to contribute to a better "sex and gender perspective" on health and healthcare in clinical practice and research. E.Wouters Editor in Chief Eur Respir Mon, 2003, 25, a. Printed in UK - all rights reserved. Copyright ERS Journals Ltd 2003 European Respiratory Monograph ISSN 1025-448x. ISBN 1-904097-28-6. a