Twenty-six patients were treated for malignant melanoma of the choroid with iodine 125 episcleral plaques. Patients were followed up for at least two years, with a mean follow-up of 45 months. Tumor shrinkage was documented by A-scan ultrasonography in all but one patient. The average reduction in tumor thickness was 46%. Visual acuity remained within two Snellen lines of preoperative levels in 14 (54%) of the 26 patients. Of the 12 patients who lost more than two lines of central visual acuity, eight developed radiation changes affecting either the optic nerve or retina, and three developed cataracts; enucleation accounted for the loss of vision in the final patient. Enucleation was necessary in one other patient in this series because of tumor growth. The mean duration between treatment with iodine 125 and the development of radiation changes affecting the optic nerve or retina was 32 months.