Twenty-three patients were treated with radon therapy for choroidal melanoma at the Ohio State University Hospitals, Columbus, between 1968 and 1976. We present an 18-year experience, including follow-up of at least eight years, in all those receiving therapy. Three patients (13%) died of metastatic disease. Four patients (17.4%) died of other causes. Sixteen patients (69.6%) were alive, with no signs of metastatic disease. Eight patients subsequently required enucleation due to inadequate tumor response. Of the 15 patients who demonstrated successful tumor destruction and retained their eyes, 13 (86.7%) developed substantial irradiation-induced retinopathy, including hard exudates, telangiectasias, neovascularization, microaneurysms, intraretinal and vitreous hemorrhages, secondary glaucoma, and irradiation-induced cataract. Our long-term results indicate a high incidence of both vascular complications and decreased visual acuity.