Background: Controversy exists regarding the use of concurrent cholecystectomy during Roux-en-Y gastric bypass performed for morbid obesity. Methods: A decision model was developed to evaluate the cost-effectiveness of current strategies: routine concurrent cholecystectomy, Roux-en-Y gastric bypass alone with or without postoperative ursodiol therapy, and selective cholecystectomy based on preoperative findings on ultrasonography. Probabilities were obtained from a comprehensive literature review. Costs and hospital days were obtained from the Healthcare Cost and Utilization Project Nationwide Inpatient Sample. One-way sensitivity analyses were performed. Results: The least expensive strategy was to perform RYGB alone without preoperative ultrasonography, with an average cost (over RYGB costs) of $537 per patient. RYGB with concurrent cholecystectomy had a cost of $631. Selective cholecystectomy based on preoperative ultrasonography was dominated by the other 2 strategies. Our model was most sensitive to the probability of developing gallbladder-related symptoms after RYGB alone. When the incidence of gallbladder-related symptoms was <4.6%, the dominant strategy was to perform a RYGB alone without preoperative ultrasonography. For values >6.9%, performing concurrent cholecystectomy at the time of the RYGB was superior to other strategies. When ursodiol was used, the least expensive strategy was to perform a concurrent cholecystectomy during RYGB. Conclusion: The main factor determining the most cost-effective strategy is the incidence of gallbladder-related symptoms after RYGB. The use of ursodiol was associated with an increase in cost that does not justify its use after RYGB. Finally, selective cholecystectomy based on preoperative ultrasonography was dominated by the other strategies in the scenarios evaluated.