OBJECTIVES: . To evaluate the cost-utility of bariatric surgery (gastric bypass, sleeve gastrectomy and gastric banding) versus ordinary treatment in health care. METHODS: . Analysis was done from health care providers' perspective using a Markov cycle tree and a time horizon of ten years. Events during the first year, including mortality and primary complications resulting in reoperation, were modelled in a decision tree. Then the patient cohort moves into a state transition model including four states: alive (no reoperation or abdominoplasty), reoperation, abdominoplasty, and death. The parameter values were taken from a large representative population survey measuring health-related quality of life (HRQoL) and health service use, as well as from registers and literature. When necessary, expert opinions were used. Different types of sensitivity analysis were conducted. RESULTS: . In CUA bariatric surgery dominated strongly the ordinary treatment. The mean cost was €31,800 and €44,800 and the mean number of QALYs 7.05 and 6.51 for bariatric surgery and ordinary treatment, respectively. Uncertainty around the parameter values was tested comprehensively in sensitivity analyses and the results were robust.  CONCLUSIONS: . The model takes into account all the major events. Strengths of the model include the actual cost data on bariatric surgery and inclusion of abdominoplasty, which seems to be neglected in previous analyses. Also, a unique set of data on mean health care costs and HRQoL for both alternatives was available. The time horizon is rather short and may underestimate the effectiveness of bariatric surgery, but it is based on available follow-up data.