Background: Gastrointestinal leak is a complication of laparoscopic Roux-en-Y gastric bypass (LRYGB). Contrast studies may underdiagnose leaks, forcing surgeons to rely solely on clinical data. This study was designed to evaluate various clinical signs for detecting leakage after LRYGB. Methods: We retrospectively reviewed 210 consecutive patients who underwent LRYGB between April 1999 and September 2001. There were nine documented leaks (4.3%). Clinical signs between patients with leaks (group 1) and those without leaks (group 2) were compared using univariate and multivariate logistic regression analysis. Results: Evidence of respiratory distress and a heart rate exceeding 120 beats per min were the two most sensitive indicators of gastrointestinal leak. Routine upper gastrointestinal contrast imaging detected only two of nine leaks (22%). Conclusion: Leak after LRYGB may be difficult to detect. Evidence of respiratory distress and tachycardia exceeding 120 beats per min may be the most useful clinical indicators of leak after laparoscopic Roux-en-Y gastric bypass.Presented in part at the 8th World Congress of Society of American Gastrointestinal and Endoscopic Surgeons (SAGES), New York, New York, USA, 13–16 March 2002