In September 2002, we invited researchers to discuss their work, but also to consolidate our knowledge of sexual segregation in vertebrates, during a three-day workshop in the Zoology Department of the University of Cambridge. The book stems from this workshop, but is much more than a compilation of different research chapters. At that workshop we gave each author the task to integrate their knowledge of a particular system into the framework of sexual segregation. Many of the authors had not even previously worked on sexual segregation but, as you will see, they all did an excellent job in synthesizing information on sexual segregation and the ecology of the two sexes in different taxa. We're very fortunate to have been able to attract so many outstanding scientists who either contributed to the book itself or commented on the chapters. Our special thanks also go to Lotti and Hans Neuhaus who flew over from Switzerland to look after Anna May, so that we did not have to segregate for parental duties. We are also very grateful to the staff at Gonville and Caius College, Cambridge, who provided accommodation for the workshop; to the University of Cambridge, who provided us with tea and biscuits during tea breaks; and, in particular, we would like to thank the staff in the Zoology Department of Cambridge and all our colleagues who supported us in various stages during the writing and editing of this book.