From 1978 to 1980, 68 patients with rectal cancer were randomly allocated to either preoperative irradiation plus surgery or surgical treatment without any preoperative measures. The primary aim of the trial was to investigate the 5-year survival rate in both groups; a secondary aim was to analyze the local recurrence rate and finally the anatomopathologic tumoral classification after surgery. All patients were followed at least 8 years. The preoperative irradiation group (Group A) was submitted to 4000 cGy for 4 weeks and surgery was performed 1 week after irradiation. All tumors were classified anatomically and pathologically according to Broders' and Dukes' classifications. The results indicated that there is a significant difference in the five-year survival rates in both groups: group A had a corrected survival rate of 80 percent; group B (nonirradiated) had a corrected survival rate of 80 percent; group B (nonirradiated) had a corrected survival rate of 34.4 percent. The local recurrence rate was 2.9 percent in group A and 23.5 percent in group B. Regarding tumor regression, before radiotherapy 64.6 percent of the tumors were Broders' Grades 3 and 4; after radiotherapy these were reduced to 20.5 percent. As to Dukes' classification, 26.4 percent of the tumors were type C in group A and, in group B, 47 percent were considered as Dukes' C.