This book is the record of the proceedings of a NATO Advanced Study Institute held in Erice, Sicily, from the 2nd - 12th June 1981, during which scientists and clinicians interested in the problems presented by cancer of the kidney and the prostate were encouraged to present, to discuss and to challenge the opinions expressed and the beliefs held by the different contributors. It is uncommon for scientist, physician, and surgeon to meet with great regularity or for prolonged periods of time and it must be exceedingly rare for such people to immerse themselves in each other's work and company for aperiod of almost two weeks. For this to occur in a situation of total isolation such as that provided by the marvellous Ettore Majorana Centre in Erice, Sicily must be unique. The fact that differences of opinion remain will be evident to all who read the book, as will the wealth of scientific and clinical work being undertaken within and beyond the NATO countries. We are very much indebted to the Science Committee of NATO for their recommendation for support for this meeting and to the Ente Fiuggi and to several pharmaceutical firms.