A review was undertaken of 360 patients undergoing elective left-sided colonic or rectal resections with primary anastomosis, under the care of one surgeon, over a nineteen year period. The incidence, aetiology and management of anastomotic leaks and strictures was studied and the role of proximal diverting colostomy considered. Perioperative mortality was 2.7%. The incidence of anastomotic leaks was 24.4%. Leaks were more common when anastomoses were low, were sutured or were constructed by trainees. Strictures developed in 5.8%. Local recurrence of tumour was the cause of 25% of these strictures. Anastomotic leakage was the principal cause of benign strictures; those developing in association with leaks were more likely to require surgical intervention. There was no evidence that delay in colostomy closure contributed to the development of benign anastomotic strictures. It was not possible to determine whether the presence of a colostomy affected the incidence of leaks but the local effects of such leaks were mitigated in patients with colostomies. Where a minor leak had occurred it was not necessary to wait for complete anastomotic healing before closing the colostomy. After major leaks, colostomy closure before complete healing was associated with further anastomotic problems in 16.0% of cases.