In February 1980 the Royal College of Radiologists, London, held its Second Symposium on Clinical Oncology. The subject was Prostatic Cancer and this publication is based on the presen tations at this meeting by leading authorities in the United Kingdom. The principal objective of these Symposia is to promote multi disciplinary collaboration for the benefit of cancer patients. Awareness and understanding of advances in a broad range of subjects are essential to ensure the timely and effective appli cation of new techniques in the prevention and treatment of all forms of cancer. Communication of this kind may also stimulate the creation of new ideas that may prove to be of more fundamental relevance to cancer research. Prostatic cancer has been afforded too little attention in the past, and its importance in Clinical Oncology has not been adequately recognised. And yet over the last 10 years consid erable progress has been recorded in our understanding of this disease and in its assessment and management. These achieve ments are well documented in this collection of papers and the outstanding problems are also clearly indicated. It is acknowl edged that the early diagnosis of prostatic cancer presents a continuing challenge, associated with the uncertainties that concern the clinical significance of 'latent' cancer of the prostate. The accurate assessment of the incidence and preva lence of the disease is extremely difficult and together these problems complicate the evaluation of the management of early or localised prostatic cancer.