An 11-year-old Caucasian girl who had been cured of bilateral retinoblastoma developed non-radiation-induced osteosarcoma in multiple sites of the extremities. Investigation of the medical histories of 36 of her family members through six generations revealed that 8 relatives on the maternal side (22%) had malignant tumors, predominately genitourinary carcinomas, 2(6%) had benign tumors only, and 2(6%) had both benign and malignant neoplasms. The histologic variety of these tumors, the predominance of genitourinary carcinoma, the higher than expected frequency of tumor appearance over six generations, and the occurrence of malignant tumors in direct lineage suggest that the case of retinoblastoma followed by osteosarcoma is part of a familial cancer syndrome.