Objectives: To evaluate the cost-effectiveness of first-line treatment of Overactive Bladder (OAB) with fesoterodine relative to mirabegron, from the Spanish National Health System (NHS) perspective. Methods: A decision tree model was developed to represent a typical clinical process of 52-week of treatment for an OAB patient with urge urinary incontinence (UUI) initiating first-line therapy with fesoterodine 4 mg, including optional titration to 8 mg, vs.mirabegron 50 mg. Efficacy data were obtained from a Bayesian indirect treatment meta-analysis. Patients with UUI of less than one episode/day were defined as treatment responder and persistence was assessed at weeks 4, 12 and 24. At week 12, non-responders discontinued treatment permanently. Quality adjusted life years (QALYs) were calculated based on time spent in responder and non-responder states. OAB-related drug and medical care costs including physician visits, laboratory tests, incontinence pads, and comorbidities (fracture, skin infection, urinary tract infections and depression) were modeled and expressed in (sic)2015. Results: At week 52, the percentage of responders was 20.8% for patients starting on fesoterodine 4 mg who optionally titrated to 8 mg and 19.4% for patients treated with mirabegron. QALYs were slightly higher with fesoterodine than mirabegron (0.7703vs. 0.7668, difference = 0.0035). Fesoterodine treatment also had slightly higher total costs than mirabegron (3,296(sic) vs. 3,217, difference= 79(sic)), resulting in a cost of 22,523/QALY(sic) gained for fesoterodine versus mirabegron. Probabilistic sensitivity analysis confirmed the slight advantage of fesoterodine with a 61.1% probability of being cost-effective at the 30,000(sic) willingness-to-pay for 1 QALY threshold. Conclusions: Given the relatively small 1-year cost difference between the two treatments, fesoterodine can be considered a cost-effective option relative to mirabegron for the first-line management of OAB with UUI in Spain. (C) 2016 AEU. Published by Elsevier Espana, S.L.U. All rights reserved.