There can be no doubt that a knowledge of cancer is becoming of increasing importance to doctors throughout the world. The changing patterns of disease incidence, following changes in living standards and public health services and in medical diagnosis and treatment, reveal the importance of neoplastic disorders as causes of morbidity and mortality. If doctors are to recognise these conditions at the earliest opportunity and advise on the treatment, they must be familiar not only with clinical appearances but with the scientific principles on which the management is based. These are so important that they must be assimilated during undergraduate medical education and become an integral part of the doctor's professional equipment. The clinical study of a neoplastic disorder has usually been related to its site of appearance in the body, and its treatment has been the concern of organ- or system-specialists. This has tended to obscure the fundamental principles of growth-disorder which are common to many varieties of tumor. A unified approach of clinical oncology can recognise common features and high-light diversity as a stimulus to further investigation. It is at the same time becoming increasingly recognised that neoplasia is a multidisciplinary problem, requiring the collaboration of many specialists: physicians, surgeons, radiotherapists, chemotherapists, pathologists, immunologists, epidemiologists, and many varieties of research worker. But the fate of the individual patient with cancer is often determined by the first doctor he consults, and this further emphasises the importance of sufficient education in oncology at all stages of medical training.