The objective of this study was to assess the role of various clinical and treatment factors involved in the long-term incidence of nonocular second primary tumors following retinoblastoma. The study was based on 111 patients treated between 1963 and 1977 according to the same radiotherapy protocol (electron beam radiotherapy) alone or in combination with triethylene melamine (TEM). Various statistical methods were used to obtain the actuarial survival curve, the cumulative incidence of second primary tumors, and comparisons of patient groups and subgroups. The 5-, 10-, 20-, and 30-year survival rates were 75%, 70%, 63%, and 55% with a follow-up of 23 to 35 years. The study reports the various parameters concerning 111 children and 17 second primary tumors: sex, age at treatment, histology of the retinoblastoma and second primary tumors, site of second tumors (anatomic and compared with irradiation field), radiation dose, time to onset, and chemotherapy with or without TEM. The results are discussed and compared with the data reported in the literature. Electron beam radiotherapy at a dose of 45 Gy does not eliminate the risk of nonocular second primary tumors. TEM also does not modify survival or the overall incidence of second primary tumors, but significantly increases the risk of second primary tumors outside the irradiation field.