Ten patients with large melanomas and one patient with recurrent retinoblastoma were treated with combined localized current field (LCF) hyperthermia and iodine 125 irradiation delivered by episcleral plaque. Tumors were heated to 43 degrees to 45 degrees C for 28 to 45 minutes. Localized current field hyperthermia when combined with irradiation appeared to induce rapid tumor necrosis. One eye enucleated 17 hours after treatment showed only focal necrosis of the melanoma, while another eye demonstrated extensive necrosis 60 hours after treatment. In all remaining eyes, tumor regression occurred within the first month of treatment. Complications included cataract formation in six eyes, hemorrhagic retinal detachment in five eyes, and phthisis in two eyes. Complications from combined therapy of large intraocular tumors in this series appeared to result from the rapid necrosis of the tumor and secondary intraocular inflammation. Intraocular temperature dosimetry measurements demonstrated a temperature gradient of not more than -0.23 degrees C/mm-1 per axial millimeter from the episcleral plaque surface to the apex of the tumor. The authors believe that LCF hyperthermia could be a suitable means of application of hyperthermia in patients with intraocular tumors if further modifications were performed to reduce ocular complications.