The authors describe five eyes in four patients with diffuse choroidal hemangiomas associated with progressive serous nonrhegmatogenous retinal detachment that were treated with low dose external beam ocular irradiation (1,250 to 2,000 cGy in multiple fractions). The subretinal fluid reabsorbed completely within 3 to 12 months of treatment in every case and there has been no reaccumulation in any case to date (median follow-up 14 months). Two of the patients have developed a focal posterior subcapsular radiation cataract in the treated eye (at 19 months and 66 months, respectively, after irradiation), but none of the patients has thus far developed radiation retinopathy. The authors discuss the potential benefits and risks of this form of treatment for choroidal hemangiomas with bullous retinal detachment.