Within the past few years photoradiation therapy has emerged as a promising new treatment for many forms of localized malignant disease and a number of clinical trials are now in progress. The pilot study described in this paper is the first clinical trial of photoradiation therapy to be carried out in Great Britain. Although it is not possible to draw significant conclusions from the results obtained, it has been shown that all the tumours responded to treatment and in four patients who had tumours which were suitable for photoradiation therapy, complete tumour regression was obtained. Further trials are in progress and others are planned in a number of centres.