OBJECTIVE To evaluate fertility in male patients with osteosarcoma after chemotherapy including high doses of alkylating agents. METHODS Postchemotherapy fertility was evaluated in 96 male patients who received chemotherapy at the authors' institution from 1976 to 1996 for localized bone osteosarcoma of the extremities. Four drugs were administrated (doxorubicin, cisplatin, methotrexate, ifosfamide) at different doses according to six different protocols. Eleven patients were prepubertal and 85 were postpubertal at the time of chemotherapy. The median age of these patients at the time of chemotherapy was 17 years (range 10-42), the median age at the time of the interview was 27 years (range 19-53), and the median follow-up from the end of chemotherapy was 9 years (range 4-17). RESULTS Of the 96 patients, 26 underwent sperm analysis and 20 showed oligo- or azoospermia. Patients who received high-dose ifosfamide showed a higher incidence of azoospermia. Six patients were normospermic and received no ifosfamide or lower doses of ifosfamide. Eight patients fathered a total of 12 children. No birth defects or congenital anomalies were observed in their offspring. CONCLUSIONS The rate of sterility was related to ifosfamide dosage. It appears that pubertal maturation is not affected by chemotherapy. No congenital malformations were seen in the children of the few patients who fathered children.