Photodynamic therapy (PDT) is finding increasing application to a number of malignant tumors. It is based on the specific photosensitization of malignant tissue by a particular porphyrin derived from hematoporphyrin, known as Photofrin II. The exact structure at present is unknown. However this material, following systemic injection, is retained longer in malignant tissue than in many normal tissues and can be activated by visible light, usually red, to initiate a lethal phototoxic effect on the tumor. It is a particularly useful treatment when specificity is necessary in treatment, for example in treatment of widespread chest wall metastasis, bladder cancer and early lesions of the bronchus, trachea and esophagus, including CIS.