OBJECTIVES: Overactive Bladder (OAB) is defined as urgency, with or without urge incontinence, usually with frequency and nocturia. The prevalence of OAB in Korea is increasing more than ever before. It is estimated at about 12.2% in adults aged over 18 years (men 10%, women 14.3%), and 14.9% in adults aged over 40 years (men 11.2%, women 18.4%). The study objective is to evaluate the cost-effectiveness of Solifenacin compared with Toterodine ER for patients with overactive bladder. METHODS: We developed a decision-analytic model to estimate treatment patterns, resource utilization, and costs for a six-month period with a societal perspective. The clinical outcome (percentage reduction in micturition frequency) and probabilities (Patient Perception of Bladder Conditions, PPBC) for the 1st cycle were collected from the literature, and the probabilities of each node for the 2nd cycle were obtained from the literature and expert opinions through the administration of a semi-Delphi survey where necessary. The cost items were limited to drugs, monitoring, OAB induced comorbidities, physical therapies, surgery, and traveling to the hospital. RESULTS: The expected cost of treating OAB patients with Solifenacin (540,170 won) is 19,872 won less costly compared with Extended-release Tolterodine (560,042 won). The Solifenacin arm also showed greater effectiveness than the Tolterodine arm in percentage reduction in micturition frequency. When we conducted a sensitivity analysis on success rate (PPBC) and outcome (percentage reduction in micturition frequency), the results showed robust. CONCLUSION: The results from this study suggest that treatment with Solifenacin dominates Extended-release Tolterodine in terms of lower cost and greater effectiveness.