Objective: The aim of this randomized multicenter trial was to assess the rate of symptomatic anastomotic leakage in patients operated on with low anterior resection for rectal cancer and who were intraoperatively randomized to a defunctioning stoma or not. Summary Background Data: The introduction of total mesorectal excision surgery as the surgical technique of choice for carcinoma in the lower and mid rectum has led to decreased local recurrence and improved oncological results. Despite these advances, perioperative morbidity remains a major issue, and the most feared complication is symptomatic anastomotic leakage. The role of the defunctioning stoma in regard to anastomotic leakage is controversial and has not been assessed in any randomized trial of sufficient size. Methods: From December 1999 to June 2005, a total of 234 patients were randomized to a defunctioning loop stoma or no loop stoma. Loop ileostomy or loop transverse colostomy was at the choice of the surgeon. Inclusion criteria for randomization were expected survival Ͼ6 months, informed consent, anastomosis Յ7 cm above the anal verge, negative air leakage test, intact anastomotic rings, and absence of major intraoperative adverse events. Results: The overall rate of symptomatic leakage was 19.2% (45 of 234). Patients randomized to a defunctioning stoma (n ϭ 116) had leakage in 10.3% (12 of 116) and those without stoma (n ϭ 118) in 28.0% (33 of 118) (odds ratio ϭ 3.4; 95% confidence interval, 1.6 -6.9; P Ͻ 0.001). The need for urgent abdominal reoperation was 8.6% (10 of 116) in those randomized to stoma and 25.4% (30 of 118) in those without (P Ͻ 0.001). After a follow-up of median 42 months (range, 6 -72 months), 13.8% (16 of 116) of the initially defunctioned patients still had a stoma of any kind, compared with 16.9% (20 of 118) those not defunctioned (not significant). The 30-day mortality after anterior resection was 0.4% (1 of 234) and after elective reversal a defunctioning stoma 0.9% (1 of 111). Median age was 68 years (range, 32-86 years), 45.3% (106 of 234) were females, 79.1% (185 of 234) had preoperative radiotherapy, the level of anastomosis was median 5 cm, and intraoperative blood loss 550 mL, without differences between the groups. Conclusion: Defunctioning loop stoma decreased the rate of symptomatic anastomotic leakage and is therefore recommended in low anterior resection for rectal cancer.