The problems associated with recurrent Crohn's disease were examined in a series of 168 patients who had undergone primary resection for this condition at the General Infirmary at Leeds from 1939 to 1968 inclusive. The overall recurrence rate was 34.2%. The risk of recurrence was less in patients with involvement mainly of large bowel rather than small. It was also affected by the age of the patient, being greatest in children or adolescents, less in adults, and least in those over 60 years of age. Recurrent disease was most commonly found in the small bowel proximal to an anastomosis, and usually manifested itself either in the first year or two after surgery or some five to 15 years later. Patients with ;early' recurrence had a shorter history of symptoms at operation, and a graver outlook than those with ;late' recurrence. The status of recurrent cases was much better than might have been anticipated in so far as nearly 70% of them were considered at review to be in very good or good general health. Moreover the risk of further recurrence after a second or third operation was found to be no greater than after a first operation.