BACKGROUND: The purpose of this study is to use nationally representative data to examine regional variations in the use and outcomes of gastric bypass surgery. METHODS: Using data from the Nationwide Inpatient Sample (NIS), we identified adults undergoing gastric bypass surgery (n = 92,910) in 2005. Following descriptive analyses, multiple logistic regression models were constructed to examine regional variations in the likelihood of laparoscopic vs. open approaches and in the likelihood of complications while controlling for patient and hospital characteristics. RESULTS: After indirectly adjusting for age and sex, the gastric bypass rates per 100,000 were as follows: Northeast, 70; Midwest, 39; South, 37; and West, 61. After adjusting for both patient and hospital characteristics, the odds of receiving laparoscopic surgery for patients living in the West were 1.79 times the mean [95% confidence interval (CI): 1.67-1.92], while the odds of receiving laparoscopic surgery for patients in the Midwest were 0.66 of the mean (95% CI: 0.62-0.70) and those of the Northeast were 0.88 of the mean (95% CI: 0.83-0.94). When adjusting for both patient and hospital characteristics, the odds of one or more postoperative complications among patients living in the South were greater than the mean (OR: 1.14, 95% CI: 1.02-1.26). CONCLUSIONS: Findings from this study suggest that gastric bypass surgery is more common in the Northeast and West. There is a greater likelihood of gastric bypass being performed laparoscopically in the West; it is less likely to be performed in the Northeast and Midwest. Postoperative complications are more likely to occur in the South.