The influence of age and sex on chemotherapy-related toxicity was evaluated in children and adults with non metastatic osteosarcoma. treatment consisted of methotrexate (MTX, 12 g/m(2)), cisplatin (CDP 120 mg/m(2)) and doxorubicin (ADM 75-90 mg/m(2)) and high-dose ifosfamide (HDIFO). toxicity data from 1,051 courses (295 with MTX, 756 based on doxorubicin, cisplatin and high-dose ifosfamide) were analyzed. Children (4-14 yrs) and females showed a higher incidence of grade 4 neutropenia and thrombocytopenia and were more frequently hospitalized for neutropenic fever compared to adolescents and young adults (AYA, 15-19 yrs) and adults (>20-40 yrs). Delayed MTX excretion was higher in adults than AYA and children. Adults (up to 40 years) can be treated with pediatric protocols for osteosarcoma and they experience lower hematologic toxicity compared to pediatric population. further investigations on sex-related susceptibility to chemotherapy in osteosarcoma patients are recommended.