Retinoblastoma is usually curable in developed countries. The morbidity and mortality of patients with hereditary retinoblastoma is still threatened by the occurrence of secondary tumours. Between 1971 and 1988, 427 patients with retinoblastoma were treated in the ophthalmologic, paediatric and radiotherapy departments of the Institut Curie. In this study, we report the clinical and therapeutic features and the outcome of 25 patients treated for a second malignant neoplasm, diagnosed between 1997 and 1999 at the Institut Curie. The median time interval between the diagnosis of retinoblastoma and SMN was 11.2 years (range 3.8-20.6 years). Histopathological diagnoses included: 12 osteosarcomas, 12 soft tissue sarcomas and, 1 malignant oligodendroglioma. The second malignant neoplasm was located inside the radiation field in 21 cases and outside in 4. Twenty three patients received pre-operative chemotherapy. Surgery was performed in 16 patients. Post-operative chemotherapy was administered in 12 patients and external beam radiotherapy was used in 2 patients. Response to treatment was evaluable in 24 patients: complete remissions were observed in 14/24, partial remissions in 2/24 and progressive disease in 8/24. Nineteen patients died. Six are still alive, with 4 in complete remission (median follow-up 8.8 years; range 5.8-13.9 years). Despite aggressive therapy, the prognosis of patients with second malignant neoplasm occurring after retinoblastoma is very poor. It is important to provide information to retinoblastoma patients regarding the risk of a second tumour as this may facilitate an early tumour detection.