The assessment of tumour response after treatment is one of the most important challenges in Oncology and the picture is so often complicated by the effects of therapy itself. Clinical assessment is still by far the most important method of assessment at our disposal but there is increasing dependence on investigations of all types as indices of response. This depen- dence may be misplaced if inappropriate investigations are pursued and we have tried to emphasise in this book the importance of selectivity. Some indices of assessment (e. g. tumour markers, organ imaging) have a vital role to play; others (e. g. histopathology, genetics) are assuming greater impor- tance as tumour behaviour becomes better understood. One subject, Immu- nology, is still in its infancy as regards tumour follow-up, but shows much promise so that a full account of tumour immunology and trends in immu- notherapy has been included. I am grateful to Dr. Brian Ross for his help with the chapter on Organ Imaging, to the Department of Medical Illustration for their ever-ready co-operation with illustrations and photographs and to Miss Shirley Francis for doing much of the typing. B. W. HANCOCK List of Contributors HANCOCK, B. W. , MD, DCH, MRCP, Senior Lecturer in Medicine, Hon- orary Consultant Physician, Royal Hallamshire & Weston Park Hospitals, Sheffield, U. K. NEAL, F. E. , KSG, MBChB, FRCR, DMRT, Consultant Radiotherapist & Oncologist, Weston Park Hospital, Sheffield, u. K. POTTER, AM.