From 1979 through 1987, 82 children with retinoblastoma were treated with primary external beam therapy, to one or both eyes. A total of 120 eyes were irradiated, with doses from 3850-5000 cGy. We used a lens-sparing electron beam technique from 1979 to 1984 and a modified lateral beam technique from 1984 to 1987. Comparison of outcome for eyes with Group I-III (Reese-Ellsworth) disease revealed a significant advantage for freedom from relapse favoring the lateral technique (p = 0.0009). A similar trend was noted for final eye outcome (need for enucleation). No differences were noted for eyes with Group IV-V disease. Patient survival was 90% at 4 years, with a mean follow-up time of 36 months.