Thermoradiotherapy (TRT) was used to treat 18 patients with choroidal melanoma. Techniques and clinical observations using a plaque-type device capable of delivering microwave hyperthermia to intraocular tumors are described. Iodine-125 plaque irradiation (48-88 Gy to apex), together with microwave hyperthermia (46 degrees-52.5 degrees C to base), were given to patients during one brachytherapy session. Since October 1985, 15 medium and 3 large-sized tumors were treated. Clinical observations include partial clearing of six vitreous opacities as well as three retinal detachments noted before treatment. Objective measurements of improved visual acuity were noted in seven of the nine cases. All tumors responded to treatment, but one tumor had regrowth and the eye was enucleated. These data suggest that a microwave plaque can be used to deliver hyperthermia to human choroidal melanomas. Within the range of the follow-up period, no side effects that might preclude the use of this hyperthermia system for choroidal melanoma treatment were noted.