From 1984 to 1997, 57 consecutive patients with non-metastatic Ewing's sarcoma of the ribs were treated according to multimodal French Society of Pediatric Oncology (SFOP) protocols EW 84, EW 88 and EW 93. The results of treatment were reviewed and analysed. Median age was 12 years. 34 patients had large tumours (greatest tumour dimension > or = 8 cm); pleural effusion was noted in 26. A tumour-positive margin after surgery was noted in 15 patients. Histological response after chemotherapy was assessed in 34 patients. 34 patients received radiation therapy. With a median follow-up of 5 years, the projected overall and relapse-free survival rates were 69 and 62%, respectively. The major site of relapse was local. None of the following was significant in predicting relapse: tumour size, gender, age at diagnosis, existence of pleural effusion, level of rib tumour, rib component, type of local control, surgical margin (positive or negative). Response to chemotherapy was the sole significant prognostic factor (P=0.004). Patients with pleural effusion had a higher percentage of relapse if they were treated without local radiation therapy. Our study confirms the prognostic significance of response to initial chemotherapy. Radiation therapy may be withheld in selected cases, but seems necessary in patients with pleural effusion.