This book is based on the proceedings of a successful Boerhaave International Symposium on colorectal cancer held at the University of Leiden, 6-9 June, 1979. I would like to offer grateful thanks to the eminent clinicians and scientists who contributed both to the Symposium and to this book. Colorectal cancer is a very common form of malignancy, particularly in the Western world, and there have been a number of recent developments in the management of this condition. This book has attempted to collate informa tion on the current methods of investigation and treatment and I believe that it will prove valuable to all those interested in oncology. The contents range widely, covering the entire field from epidemiology through screening methods, diagnostic approaches and therapy of both primary and secondary disease. Perhaps the most outstanding new areas discussed and reflected in the proceedings are the possible range and scope of screening techniques, the new possibilities both in treatment and in endoscopic surgery now available as a result of developments in fibre-optic endoscopy, and new approaches and important parameters in staging of the disease.