Background: Small bowel obstruction (SBO) is a recognized complication of open bariatric surgery; however, the incidence after laparoscopic procedures is not clearly established. This paper reviews our experience with small bowel obstruction after laparoscopic Roux-en-Y gastric bypass. Methods: Between 1995 and 2001, 711 (246 antecolic, 465 retrocolic) patients underwent a laparoscopic proximal divided Roux-en-Y gastric bypass via the linear endostapler technique. 13 patients (1.8%) developed SBO requiring surgical intervention.There were 11 females and 2 males, ages 29-60 (mean 38), with mean weight 126 kg (range 105-188), and mean BMI 50 (range 41-59). 7 obstructive patients (55%) had undergone previous open abdominal surgery. Median time to obstruction was 21 days (range 5-1095). Mean follow-up of all patients is 43 months (range 3-79). Results: Etiology of obstruction was internal hernia - 6, adhesive bands - 5 (only 2 were related to prior open surgery), mesocolon window scarring - 1, and incarcerated ventral hernia - 1. The incidence of SBO was 4.5% (11/246) in the retrocolic group, and 0.43% (2/465) in the antecolic group, which was highly significant (P=.006). 1 adhesive patient required an open bowel resection for ischemia. There was 1 death. Conclusion: SBO occurred with an overall incidence of 1.8% in a large series of laparoscopic gastric bypass patients, and was associated with a high morbidity. A significant decrease in occurrence was found after adoption of antecolic placement of the Roux limb.