Thirty-three infants ( < 1 year at diagnosis) were treated for retinoblastoma with primary irradiation at St. Jude Children's Research Hospital (SJCRH) between 1963 and June 1992. Staging of the 44 treated eyes was as follows: Reese-Ellsworth (R-E) Groups I (n = 20), Group II (n = 9), Group III (n = 6), Group IV (n = 2), Group V (n = 7). Irradiation was delivered using either a single anterior field (31 eyes) or lens-sparing techniques (13 eyes). Total doses ranged from 21-45 Gy (median = 36 Gy) in fractions of 150-180 cGy (n = 34) or > 180 cGy (n = 10). One child died of metastatic disease at 42 months. Three patients have developed second malignant neoplasms; two have succumbed at 88 and 125 months post-RB diagnosis; the remaining patients are alive at 6-259 months postdiagnosis (median follow-up = 127 months). Local control with irradiation alone and supplemented cryotherapy given within 2 months (n = 2) was maintained in 29 eyes, with no statistical difference seen for total doses < or = 36 Gy (21/8 eyes) vs. > 36 Gy (8/16). Of 15 eyes that required salvage therapy, tumor control has been maintained in 13. Enucleation was required for four patients, two with recurrent retinoblastoma and one with a phthisical eye. Cataract formation was documented in 23 eyes (87.5%) treated with lens-sparing techniques developed cataract. At last follow-up, 23 of 30 patients tested (77%) had visual acuity of 20/100 or better. This experience confirms early observations in that doses > or = 36 Gy do not appear to improve local control with irradiation alone in infants ( < 365 days) with retinoblastoma.