['The aim of the present study was to compare the influence of preoperative chemoradiotherapy (CRT) with postoperative CRT on the incidence and types of postoperative complications in rectal cancer patients who underwent sphincter-saving resection.', 'We reviewed 285 patients who received preoperative CRT and 418 patients who received postoperative CRT between January 2000 and December 2006.', 'There was no between-group difference in age, gender, or cancer stage. In the pre-CRT group, the mean level of anastomosis from the anal verge was lower (3.5 +/- 1.4 cm vs. 4.3 +/- 1.7 cm, p < 0.001) and the rate of T4 lesion and temporary diverting ileostomy was higher than in the post-CRT group. Delayed anastomotic leakage and rectovaginal fistulae developed more frequently in the pre-CRT group than in the post-CRT group (3.9% vs. 1.2%, p = 0.020, 6.5% vs. 1.3%, p = 0.027, respectively). Small bowel obstruction (arising from radiation enteritis) requiring surgical intervention was more frequent in the post-CRT group (0% in the pre-CRT group vs. 1.4% in the post-CRT group, p = 0.042). Multivariate analysis identified preoperative CRT as an independent risk factor for fistulous complications (delayed anastomotic leakage, rectovaginal fistula, rectovesical fistula), and postoperative CRT as a risk factor for obstructive complications (anastomotic stricture, small bowel obstruction). The stoma-free rates were significantly lower in the pre-CRT group than in the post-CRT group (5-year stoma-free rates: 92.8% vs. 97.0%, p = 0.008).'] Is complications after sphincter-saving resection in rectal cancer patients according to whether chemoradiotherapy performed before or after surgery?