OBJECTIVES: The aim of this study was to assess the cost-effectiveness of solifenacin (5mg/10mg) relative to tolterodine ER 4mg in the treatment of patients with overactive bladder (OAB), from the perspective of the UK (NHS) health care system. METHODS: This was a cost-utility analysis based on a one-year decision-tree model. A systematic review and meta-analysis of efficacy data was performed to obtain estimates for clinical effectiveness. The benefits of treatment were measured according to resolution of OAB symptoms and subsequent improvement in health-related quality of life (HRQoL). Treatment success was defined separately for urgency, frequency and incontinence. Definitions of treatment success were no urge episodes, eight or fewer micturitions and no incontinence episodes per 24 hours respectively. Incremental cost-effectiveness ratios (ICERs) were estimated separately for each symptom.  HRQoL values were taken from published sources. Treatment persistence data and data for the proportion of solifenacin patients receiving the higher dose, 10-mg formulation were obtained from the DIN-LINK database. The analysis was undertaken from the perspective of the UK NHS and included costs directly associated with the treatment of OAB, i.e. cost of antimuscarinics, GP consultations and consultations in an outpatient clinic; cost data was taken from NHS published sources (at 2007/2008 prices). Resource utilisation was based on expert opinion. RESULTS: ICERs fell below £15,000/QALY in all analyses: £6,406/QALY, £9,065/QALY and £14,374/QALY for urgency, frequency and incontinence outcomes, respectively. ICERs remained below the threshold of £30,000/QALY throughout univariate sensitivity analyses. CONCLUSIONS: Treatment with solifenacin 5mg/10mg is likely to be a cost-effective treatment strategy relative to tolterodine ER 4mg in the UK healthc are setting.