One hundred and twenty-one consecutive patients with monostotic Ewing's sarcoma (ES) were treated according to three consecutive combined modality programs from 1974 to 1986. Their 3-year progression free survival (PFS) rate from diagnosis of 59% was identical to the event free survival (EFS) rate, since all the 50 events occurring within 3 years from diagnosis were tumor recurrences. Primary tumor was treated with radiotherapy in 75 cases, surgical resection plus radiotherapy in 38, and radical surgery in 8. Chemotherapy was given to all patients and each program included adriamycin, vincristine, and cyclophosphamide +/- dactinomycin. Median follow-up was 12 years, ranging from 6 to 19 years. The PFS rate decreased to 49% at 6 years and plateaued at 46% after the 7th year from diagnosis, even though some relapses were observed as late as 14 years from diagnosis. Second malignancies developed in 7 patients free from progressive ES and were represented by osteogenic sarcoma in previously irradiated bone in 4 cases and by breast carcinoma in 3. No other event but tumor relapse or second malignancy occurred in this series. EFS rate was 47% at 6 years and 39% at 12 years, further decreasing in the following years because of a number of late events. A continuous PFS longer than 7 years may be consistent with cure in the majority of patients with monostotic ES. However, these patients should be followed indefinitely because of risk of second malignancies.