INTRODUCTION S. Buist, C.E. Mapp, A. Rossi The idea for this monograph came out of a chance conversation that I had with the Editor in Chief, at the time, A. Rossi. I was musing on the unexpected findings about sex and gender-based differences in the Lung Health Study. We had found that airways hyperresponsiveness to methacholine was more common in women than men (later found to be largely, but not entirely, size related), that women had more difficulty quitting smoking than men and that smoking may be more harmful for women than for men. This led to a discussion about the dearth of information that is available on sex and gender-related differences in pulmonary diseases and the need for more information. A. Rossi contacted C.E. Mapp, asking her to join in the project to edit a monograph on respiratory diseases in women and she was enthusiastic about the proposal. The purpose of this monograph is to explore the relatively unexplored territory of respiratory diseases specifically in women. Until relatively recently, some respiratory diseases, such as lung cancer and chronic obstructive pulmonary disease (COPD), were thought of as diseases that preferentially affected men, the implication being that men are susceptible to these diseases or, conversely, that women are protected from them. Knowledge about the cause of these diseases led, of course, to the realisation that susceptibility was related to differences in exposure to specific risk factors, in this case to cigarette smoking. The role of sex or gender in physiological function, disease and response to treatment is gradually being explored. In the process, more and more is being learned about differences between the sexes that help to explain differences in disease prevalence, disease manifestations and response to disease and treatment. There is now recognition that sex influences virtually every biological function, either directly or indirectly. Different terms are often now used to separate differences between the sexes that are based on biological differences (sex related) from those based on sociocultural differences (gender related). Inevitably the terms "sex" and "gender" are often used loosely and interchangeably. This semantic confusion is not important. Much more important is that this topic is receiving the attention it deserves and that we are learning a lot about how biological and sociocultural differences can profoundly affect every aspect of our health and our response to disease and treatment. One practical consequence of this new realisation is that researchers now study both females and males, looking for differences that are not simply related to size. For example, women are now included in clinical trials when, in the recent past, many major trials enrolled mostly men. Another example is that attention is being paid to differences between the sexes in use of healthcare and in response to medications. Sex and gender differences are recognised as being as important as racial and ethnic differences. In this Monograph, we have invited several authorities to write about the effect of sex or gender in their specific area of interest. We have divided up the monograph into chapters that address general topics, such as sex differences in the anatomy and physiology of the lungs, chapters that address specific diseases, such as tuberculosis, COPD, asthma, occupational lung disease and lung cancer and chapters that address gender-related differences in behaviours, such as adherence to medication. This monograph should remind us that women and men and girls and boys are indeed Eur Respir Mon, 2003, 25, b–c. Printed in UK - all rights reserved. Copyright ERS Journals Ltd 2003 European Respiratory Monograph ISSN 1025-448x. ISBN 1-904097-28-6. b