The study protocol was approved by the institutional review boards of the University of Miami School of Medicine, Miami, Fla, and the University of California at San Francisco School of Medicine, San Francisco. The clinical records of all patients who received EBR as primary treatment of retinoblastoma from January 1, 1989, through December 31, 1996, were reviewed. Data collected include age at diagnosis of retinoblastoma, sex, family history of retinoblastoma, Reese-Ellsworth stage of retinoblastoma at diagnosis, presence or absence of vitreous seeds, retinal detachment, optic nerve involvement, macular involvement, technique of EBR used, total radiation dose, salvage therapy administered (including direct laser photocoagulation, transpupillary hyperthermia, and/or cryotherapy), tumor progression or recurrence, new tumor development, whether enucleation was performed, and complications (including cataract, midfacial hypoplasia, radiation retinopathy, ptosis, restrictive strabismus, secondary tumor, and metastasis). The RLS and MLB techniques included treatment to the 95% isodose line, with a total dose goal of 45 Gy at 1.8 Gy per fraction. The practice at one clinic was exclusively RLS, and the practice at the other was exclusively MLB; therefore, assignment of EBR technique was according to the clinic at which the patient received treatment. Length of follow-up was calculated from the date of the last EBR administration to the date of the most recent examination under anesthesia.