70 patients presenting to a surgical unit with radiation enteritis were followed up. 11 of the 61 who underwent operations died of operation-related causes. The 51 patients who survived for more than 3 months were followed up for up to 12 years (median 12 months). 24 had no further symptoms related to their radiation enteritis. The other 27 patients had persistence of symptoms, postoperative complications, new radiation-related problems, or a combination of these. The twenty new radiation-related problems were stricture (8 patients), malabsorption (5), fistula (1), and miscellaneous (6). These developed in 12 of 36 patients presenting initially with stricture, compared with 8 of 9 patients presenting with a perforation or fistula (p = 0·007 Fisher's exact test) and none whose first symptom was bleeding (p = 0·001 vs perforation and fistula combined). 10 of the 27 patients with further problems required operations and 5 of them died. Radiation enteritis is thus a progressive disease, with further complications becoming apparent in about half of those surviving the initial lesion. Perforation or fistula formation indicates a poorer prognosis than does stricture or haemorrhage.