OBJECTIVE: To use a simulation model to estimate the costs and benefits of bariatric surgery among full-time employees. STUDY DESIGN: Multivariate regression analysis of nationally representative survey data sets to estimate the costs of obesity and a simulation model of the number of years until breakeven under alternate assumptions about the costs and benefits of bariatric surgery. METHODS: We used a 2-part model to estimate medical costs of obesity based on the 2000-2001 Medical Expenditure Panel Survey. We estimated work loss with a negative binomial regression based on the 2002 National Health Interview Survey. Using these results, we simulated the expected number of years required for a bariatric surgery procedure to become cost saving. RESULTS: Nine percent of the full-time US workforce, or 29% of the obese workforce, is eligible for bariatric surgery. Obese workers eligible for bariatric surgery have 5.1 (P < .01) additional days of work loss and USD 2230 (in 2004 dollars) (P < .01) higher annual medical costs than persons of normal weight. CONCLUSION: Although the cost implications of bariatric surgery among full-time employees depend on many factors, the simulations reveal that 5 or more years of follow-up are most likely required for these operations to become cost saving unless the employee bears a significant fraction of the total costs of the surgery.