Comparison of the radioisotopes of iodine and gold was made by a controlled trial treating lymph node metastases from VX2 tumor in the rabbit by the endolymphatic route. Control animals received tumor inoculation only, and 2 further groups received either 4mCi 131I radioiodine in ultrafluid lipiodol or 8mCi Au198 colloidal radiogold. The primary tumor was excised at 8 to 10 days after inoculation in all animals. Pelvic node weight was the main factor on which the trial was assessed. A significant difference in node weight was found between the treated and control groups, but there was no significant difference between the treated groups. No significant increased incidence of lung metastases was found in animals receiving endolymphatic infusions.