The eighth annual multidisciplinary symposium on clinical oncol ogy organised by the Royal College of Radiologists discussed the subject of investigational techniques in oncology. It was held in London in February 1986. This volume collects together the edited texts of the papers which were presented at the meeting, together with the George Edelstyn memorial lecture given by Professor J. Einhorn. Clinicians rely very heavily on pathologists and radiologists to help with the diagnosis and staging of patients who present with malignant tumours. The conventional techniques to which we have become accustomed are fast being supplemented by exciting new approaches. These have moved very rapidly from being purely experimental techniques to being a part of routine clinical practice. Some of these new approaches have been highlighted in this symposium. Recent advances in molecular biology have produced various specific techniques for looking at phenotypic changes in cells as detected by immunohistochemical probes. Visualisation of genes and their transcripts in human biopsies has become a real possibility using a wide and increasing range of molecular probes. Some of the advantages of these techniques and their potential for the future are presented here.