Pre-operative irradiation in operable cancer of the rectum remains controversial. This is a report of a retrospective study about 192 patients treated between 1958 and 1980 at the Institut Curie (Paris) for a rectal cancer. An abdomino-perineal resection was done in 144 patients, 83 as a primary procedure and 61 after a pre-operative irradiation. During the same period 48 patients had an anterior resection. We put in this study the only patients who underwent curative surgery. Irradiation was given with high voltage by a four field "box technique". The tumour received 40 to 50 grays in 5 to 6 weeks. The operation was done at least 6 weeks after the end of the irradiation. There was no difference for the sex, and age of the patients, and in the size of the tumour before treatment, between the patients irradiated and those operated on as a primary procedure. There was no difference in the operative mortality as well as the 3, 5, and 10 year survival in the two groups. Pre-operative irradiation did not change the number of perineal recurrences or the number of visceral metastases. The healing of the perineum was significantly longer in the irradiated patients (p less than 0.001). The survival was closely related to the Dukes classification. The number of Dukes A patients was significantly higher (p = 0.02) after irradiation: 26/61 (43%) vs 19/83 (23%) when the patients were not irradiated. In our experience pre-operative irradiation can shrink some large tumours helping the surgical act.(ABSTRACT TRUNCATED AT 250 WORDS)