This book aims to describe the current state of knowledge and possible future developments in a number of major areas of research into the nature, causes and treatment of cancer. The contributing authors have been encouraged to discuss their subjects at the molecular level. It will become apparent to the reader that considerable developments in the understanding of the fundamental nature of cancer, in molecular terms, are constantly being made. This is particularly the case in the area of oncogene research where differences between tumour and normal cells can now be defined in terms of altered expression of DNA sequences. An understanding of the methods available for detecting cancer, of the process of carcinogenesis and of the means available for treating cancer can only be achieved with a precise knowledge of the basic biochemical and molecular processes involved. Since it is all to easy for the research scientist to become totally absorbed within the specialised area of research in which he is involved, the first chapter is an attempt to encourage a broader field of vision by introducing the clinician's view of the cancer problem, which illustrates the broad spectrum of basic problems that need to be solved by the cancer researcher.