Anastomotic leaks following colorectal surgery may be divided into those which are clinically significant and those which are not. Leakage occurs in 3.4-6% of all colorectal cases. It is most commonly associated with rectal anastomoses, being clinically significant in 2.9-15.3% of cases. Mortality following a leak may be 6.0-39.3%. There is no evidence that preoperative bowel preparation reduces the rate and consequences of leaks. There is no evidence for the use of drains when an anastomosis has been made outside the pelvis, but pelvic drainage may be important after anterior resection. The use of covering stomas has not been shown to reduce leak rate but does mitigate the clinical effects of leaks. Prompt diagnosis and further laparotomy can reduce mortality following leakage. Intra-abdominal abscesses can in most cases be treated by radiologically guided drainage. Anastomotic leaks are the most common cause of anastomotic strictures and are also associated with increased rates of local recurrence of cancer.