Laparoscopic Roux-en-Y gastric bypass (RYGB) and laparoscopic adjustable gastric banding (AGB) are 2 of the most commonly performed bariatric procedures worldwide. However, few large, multisite studies have directly compared the benefits and harms of these procedures. To compare the effect of laparoscopic RYGB vs AGB on short- and long-term health outcomes. A retrospective cohort study of 7457 individuals 21 years or older who underwent laparoscopic bariatric surgery from January 1, 2005, through December 31, 2009, with follow-up through December 31, 2010. All individuals were participants in the Scalable Partnering Network, a network of 10 demographically and geographically distributed health care systems in the United States. The primary outcomes were (1) change in body mass index (BMI), (2) a composite end point of 30-day rate of major adverse outcomes (death, venous thromboembolism, subsequent intervention, and failure to discharge from the hospital), (3) subsequent hospitalization, and (4) subsequent intervention. We identified 7457 patients who underwent laparoscopic AGB or RYGB procedures with a median follow-up time of 2.3 years (maximum, 6 years). The mean maximum BMI (calculated as weight in kilograms divided by height in meters squared) loss was 8.0 (95% CI, 7.8-8.3) for AGB patients and 14.8 (95% CI, 14.6-14.9) for RYGB patients (P < .001). In propensity score-adjusted models, the hazard ratio for AGB vs RYGB patients experiencing any 30-day major adverse event was 0.46 (95% CI, 0.27-0.80; P = .006). The hazard ratios comparing AGB vs RYGB patients experiencing subsequent intervention and hospitalization were 3.31 (95% CI, 2.65-4.14; P < .001) and 0.73 (95% CI, 0.61-0.88; P < .001), respectively. In this large bariatric cohort from 10 health care systems, we found that RYGB resulted in much greater weight loss than AGB but had a higher risk of short-term complications and long-term subsequent hospitalizations. On the other hand, RYGB patients had a lower risk of long-term subsequent intervention procedures than AGB patients. Bariatric surgery candidates should be well informed of these benefits and risks when they make their decisions about treatment.