The subject of this publication, thyroid cancer, was the topic chosen for the First Symposium on Clinical Oncology, orga nized by the Royal College of Radiologists, London, on 26 and 27 January 1979. The papers collected here are based on the presentations made at that meeting, but have been expanded in most cases to provide a more complete review. Thyroid cancer is an uncommon tumor, but as a result of well-directed collabora tive efforts our knowledge of its pathogenesis, natural history, and management has increased enormously in the last decade. Consideration of this progress in our understanding of thyroid cancer well illustrates the main theme to be promoted in this and future symposia, which is the encouragement of a multidisciplinary approach to the solution of the many out standing problems in clinical oncology. The need is recog nized for close and sustained collaboration between clinicians of many speciality groups and research workers of many scientific disciplines, to accelerate further progress in the prevention, early detection, and management of all forms of malignant disease. Thyroid cancer provides an excellent example of the present achievements of such a multidisciplin- VI Preface ary approach, where British research and experience have made a contribution that has received world wide recognition.