The retrospective case-control approach provides a powerful method for studying rare events and their dependence on explanatory features. The method is extensively used in epidemiology to study disease incidence, one of the best known and early examples being the investigation by Bradford Hill and Doll of the possible impact of smoking and pollution on lung cancer. More recently the approach has been ever more widely used, by no means only in an epidemiological setting. There have also been various extensions of the method.

A definitive account in an epidemiological context was given by Breslow and Day in 1980 and their book remains a key source with many important insights. Our book is addressed to a somewhat more statistical readership and aims to cover recent developments. There is an emphasis on the analysis of data arising in case-control studies, but we also focus in a number of places on design issues. We have tried to make the book reasonably selfcontained; some familiarity with simple statistical methods and theory is assumed, however. Many methods described in the book rely on the use of maximum likelihood estimation, and the extension of this to pseudolikelihoods is required in the later chapters. We have therefore included an appendix outlining some theoretical details.

There is an enormous statistical literature on case-control studies. Some of the most important fundamental work appeared in the late 1970s, while the later 1980s and the 1990s saw the establishment of methods for case-control sampling in time.