Approximately 2% of the Swiss population will develop rectal carcinoma during their lifetime. Most important prognostic factors are TNM category and quality of the surgical procedure. In advanced rectal carcinoma postoperative combined radio-chemotherapy reduces the rate of local recurrence by at least 50 percent and leads to a survival benefit of ca. 10-20%. However, preoperative radiotherapy (+/- chemotherapy) should be the treatment of choice as an adjunct to surgery, especially in cases of deep seated or fixed carcinomas. Intraoperative RT represents a promising modality in situations where a histologically complete excision of the tumor seems impossible.