BACKGROUND: There are several options for management of ciliary body melanoma, including plaque radiotherapy, charged particle irradiation, local resection, and enucleation. The choice of therapy depends on many factors, and plaque radiotherapy is often used. OBJECTIVES: To determine the outcome of plaque radiotherapy in the management of ciliary body melanoma and to identify the risk factors associated with the development of radiation complications, tumor recurrence, metastasis, and melanoma-related death after plaque radiotherapy of ciliary body melanoma. METHODS: We analyzed the clinical records of 136 patients with ciliary body melanoma who were treated with plaque radiotherapy between July 1976 and June 1992. RESULTS: The median follow-up period was 70 months. Using Kaplan-Meier survival estimates, the most frequent radiation complication at 5 years' follow-up was cataract, developing in 48% of the patients, followed by neovascular glaucoma (21%), retinopathy (20%), scleral necrosis (12%), and vitreous hemorrhage (11%). Visual acuity decrease (by > or =3 Snellen lines) was noted in 40% of the patients at 5 years. Kaplan-Meier estimates showed that 8% of the patients developed recurrence, 28% had metastasis, and 22% died of melanoma-related causes by 5 years. Univariate analysis demonstrated that the factors predictive of radiation cataract were superonasal (P = .003) and inferior tumor meridian (P = .02) compared with inferonasal meridian and apex dose rate greater than 57 cGy/h (P = .05). The development of neovascular glaucoma was significantly related to iris involvement with the ciliary body tumor (P<.001). The factors predictive of development of radiation retinopathy were base dose rate greater than 230 cGy/h (P = .03) and the presence of diabetes mellitus (P = .05). The only predictor of metastasis was tumor thickness greater than 7 mm (P = .02). The risk factors for melanoma-related death were the presence of metastasis (P<.001), tumor thickness greater than 7 mm (P = .02), and recurrence (P = .02). Multivariate analyses showed that the most significant variables predictive of the development of scleral necrosis were intraocular pressure greater than 15 mm Hg (P<.001) and tumor thickness greater than 7 mm (P = .007). The most significant predictive factors for vitreous hemorrhage were visual acuity of 20/40 to 20/200 (P = .02) and intraocular pressure greater than 15 mm Hg (P = .02). The best subset of independent predictors of vision decrease were mushroom tumor shape (P = .002), age older than 61 years (P = .006), and superonasal meridian (P = .04). The risks for melanoma-related death were presence of metastasis (P<.001) and tumor thickness greater than 7 mm (P = .01). There was no group of significant variables predictive for radiation cataract, neovascular glaucoma, retinopathy, tumor recurrence, and metastasis in multivariate analysis. CONCLUSIONS: Plaque radiotherapy offers 92% 5-year local control rate for ciliary body melanoma. Metastasis occurs in 28% of the patients treated with this method by 5 years. Patients with tumors greater than 7 mm in thickness are at greater risk than patients with thinner tumors for metastatic disease and melanoma-related death. Major radiation complications include radiation cataract, neovascular glaucoma, retinopathy, and scleral necrosis.