The treatment of malignant melanoma by a combination of surgery and endolymphatic isotopic therapy is based on experimental evidence that the dose of irradiation delivered by this route will destroy microscopic-sized deposits of cancer.4 In lymph nodes bearing cancer, there is marked destruction of melanoma in the lymph nodes after the endolymphatic administration of 40 mc of I131 ethiodol. This has been accomplished with no demonstrable interference to lymph flow due to marked differences in sensitivity to irradiation of the lymph nodes and the lymphatic vessels. The lymph nodes are radiosensitive, and the lymphatic vessels are radioresistant. Endolymphatically administered I131 ethiodol delivers a sufficient irradiation (50,000 to 100,000 rads β) to the lymph nodes in humans to destroy microscopicsized deposits of melanoma cells lodged within the lymph nodes. The primary melanoma is treated by orthodox surgical techniques. Patients classified as clinical Stage I receive no additional surgery, but receive I131 endolymphatically, and are thus spared the trauma of a radical axillary or groin dissection and their ensuing complications. A 3 year survival rate in a small group of patients with clinical Stage 1 of 85 per cent is encouraging. Patients with Stage II melanoma are treated by a combination of endolymphatic isotopes and surgical removal of the primary melanoma and the lymph nodes. The penetration of the irradiation from the administered isotope is not sufficient to depend upon such irradiation to destroy the cancer. In such instances, irradiation of lymph nodes outside the field of surgery, irradiation of any lymph nodes inadvertently left behind and irradiation to cancer cells within the lymphatics offer an additional dimension in the treatment of these patients. A 3 year survival rate of 50 per cent in a small group of patients so treated seems promising. Several patients with satellitoses have markedly benefited from endolymphatic isotope therapy. Two patients with distant metastases so treated have shown no improvement and endolymphatic isotopes are not indicated for such patients. Only by continued clinical trial, preferably on a randomized basis, can the exact role of the endolymphatic administration of radioisotopes be obtained. In England, the Medical Research Council is sponsoring such a study. At the Hunterian Lecture delivered at the Royal College of Surgeons in London, Edwards spoke about the accomplishments of endolymphatic isotopes for malignant melanoma and concluded his lecture with the following note: "There is no reason why this illness cannot be fully documented in each case arising in Great Britain and the details analysed by experts in this field. It would surely be an advance in the concept of treating malignant disease and something of which Hunter would have approved."9