Preface than in, say, molecular biology or proteomics. Largely because of this ontological fact, because biotechnologies generate and drive different types and amounts of information and research, and for other reasons, today epidemiological thinking continues to create new approaches, research designs, strategies of analysis, and causality for such biological disciplines. Thus the influence of epidemiology continues. The potential to improve the health of citizens is there. In fact, the rationale for task (2) mentioned above also includes the relevance of epidemiological methods for research on the public health problems that are best tackled by blending the reasoning and the tools of epidemiology and of some of the social sciences. Therefore, this new edition aims at being useful not only to classic epidemiological and clinical research, but would also like to continue favoring the integration of epidemiology into"microbiological"and "macrosocial"health research and practice. I am confident and content that much of this is already happening, and thus feel this book is rather in harmony ith most of the contemporary scientific world: wide open and interconnected- much more creative, relevant, efficient, and interesting because of the porousness and plasticity of the disciplines than because of the putative higher mission or language of their leaders and disciples. In short, if you live in a foreign land and have come to visit this book from "outside "epidemiology, be welcome. If you are an epidemiologist on the eve of atrip"to a foreign discipline, please take this book with you. And, again, if you mostly work"inside"epidemiology, please keep it at hand: this is your territory- yet I hope you will here discover new landscapes of unsuspected beauty. January 2008 barcelonathan in, say, molecular biology or proteomics. Largely because of this ontological fact, because biotechnologies generate and drive different types and amounts of information and research, and for other reasons, today epidemiological thinking continues to create new approaches, research designs, strategies of analysis, and ways to assess causality for such biological disciplines. Thus the infl uence of epidemiology continues. The potential to improve the health of citizens is there. In fact, the rationale for task (2) mentioned above also includes the relevance of epidemiological methods for research on the public health problems that are best tackled by blending the reasoning and the tools of epidemiology and of some of the social sciences. Therefore, this new edition aims at being useful not only to classic epidemiological and clinical research, but would also like to continue favoring the integration of epidemiology into “microbiological” and “macrosocial” health research and practice. I am confi dent and content that much of this is already happening, and thus feel this book is rather in harmony with most of the contemporary scientifi c world: wide open and interconnected— much more creative, relevant, effi cient, and interesting because of the porousness and plasticity of the disciplines than because of the putative higher mission or language of their leaders and disciples. In short, if you live in a foreign land and have come to visit this book from “outside” epidemiology, be welcome. If you are an epidemiologist on the eve of a “trip” to a foreign discipline, please take this book with you. And, again, if you mostly work “inside” epidemiology, please keep it at hand: this is your territory— yet I hope you will here discover new landscapes of unsuspected beauty. Miquel Porta January 2008 Barcelona Preface xii