In intraoperative radiation therapy (IORT) a high dose of radiation is delivered to the tumor or to the tumor bed, thus favouring local control with no significant increase in toxicity. At present it is used to deliver a boost dose of radiation for rectal cancer in protocols which include preoperative external beam radiation therapy (ERT). From various experiences carried out in a number of centers, the technical and methodological features of this procedure have been defined also relatively to cost-effectiveness in terms of a longer surgical treatment, involved specialized staff and resources. At the 5th IORT International Congress held in Lyon in September, 1994, of over 70 clinical studies reported, 15 were on rectal cancer with about 700 patients undergoing IORT. The growing interest in the use of this procedure in rectal cancer is explained by the natural history of the disease, burdened with a high rate of local recurrence, and by the possibility of preventing it with high doses of radiation. In primary tumors unresectable for cure and in local recurrence it is evidenced that ERT+surgery+IORT enable an improvement in local control and survival as compared to ERT alone. Results are better when surgery is radical. Several studies deal with the role of preoperative combined concomitant radiochemotherapy which can favour a radical surgery. A sizeable percentage of these patients will present with metastasis, thus adjuvant chemotherapy seems suitable. A role of IORT is envisaged also for resectable high risk tumors, however results should be confirmed by larger clinical series.