Abstract Aims: To report outcomes of adults with retroperitoneal sarcoma (RS) treated by surgery, external beam radiotherapy (EBRT) and intraoperative electron beam radiotherapy (IORT). Methods: From July 1988 to February 2001; 24 patients with primary and recurrent RS were diagnosed and treated. The median dose and energy of IORT delivered was 15 Gy/9 meV. EBRT dose varies between 45–50 Gy. Results: There were five primary and 19 recurrent tumours. One primary and five recurrent tumours underwent R0 resection. There were 12 liposarcomas and 19 grade I tumours; 13 patients developed local recurrence and three developed distant metastases. Twenty-two patients received IORT associated with EBRT: 11 developed recurrences. Six patients developed Neurotoxicity (4 grade II and 2 grade III). Disease free survival and overall survival at 5 years was 28 and 56% respectively. Conclusions: EBRT with IORT treatment is a promising technique for local control. Lower recurrence rates are associated with radical (R0) surgical procedures.