Although linear surgical staple line reinforcement has been shown to increase anastomotic tensile strength in animal models and reduce the incidence of staple line bleeding and anastomotic leaks in colorectal surgery, the benefits of staple line reinforcement on circular stapled anastomoses in bariatric surgery remain unreported in the literature. The purpose if this study was to compare the incidence of anastomotic bleeding, leak, and stricture in patients undergoing laparoscopic gastric bypass with circular staple line reinforcements with those with no circular staple line reinforcements. Since May 2006, 138 consecutive patients (Group B) have undergone laparoscopic Roux-en-Y divided gastric bypass with a 25-mm circular stapled gastrojejunal anastomosis using GORE SEAMGUARD bioabsorbable circular staple line reinforcement (CBSG) with a mean follow up of 9 months. The incidence of anastomotic bleeding, leak, and stricture was compared with 255 similar patients (Group A) who underwent surgery before May 2006 without gastrojejunal reinforcement with a mean follow up of 22 months. The rates of anastomotic bleeding, leak, and stricture for Group B versus Group A were 0.7 per cent versus 1.1 per cent (P = 0.64); 0.7 per cent versus 1.9 per cent (P = 0.34); and 0.7 per cent versus 9.3 per cent (P = 0.0005), respectively. The use of CBSG reduced the incidence of anastomotic stricture by 93 per cent and the incidence of a composite end point of all anastomotic complications by 85 per cent. Our results indicate that the use of circular staple line reinforcement at the gastrojejunal anastomosis in patients undergoing laparoscopic gastric bypass significantly decreases the incidence of anastomotic stricture and a composite end point of all anastomotic complications. On this basis, strong consideration should be given to the routine use of CBSG staple line reinforcement in patients undergoing laparoscopic divided gastric bypass with a circular stapled gastrojejunal anastomosis.