OBJECTIVES: The age related prevalence of Overactive Bladder in developed economies is estimated at 17% and is comparable with common diseases including depression, osteoporosis, and COPD. The burden of OAB is likely to grow in the future. The objective of this research is to estimate current and future burden of this condition using the UK as an example. METHODS: Age and sex related prevalence rates have been applied to current and forecast population data to estimate future prevalence. A published assessment of patient costs is used to derive an estimate of economic burden. RESULTS: Our analysis indicates that 4.7 million people are estimated to have OAB in the UK. Although few males are treated for this disease, male prevalence is estimated to account for up to 45% of the total (treated and untreated) OAB population. UK government population forecasts for 2020 imply a 27% growth in OAB prevalence with male prevalence increasing faster than that of females. Using published data for average annual patient costs for OAB patients, the current cost burden of OAB in the UK is estimated to exceed £800m per annum. CONCLUSIONS: OAB is a highly prevalent condition imposing a substantial economic burden, which will increase with demographic shifts towards an aging population. If the prevalence of OAB risk factors including diabetes, smoking, and UTIs increases over time, then it is reasonable to expect that age related OAB prevalence will increase with time. Our forecast prevalence may therefore under-estimate future burden because our analysis assumes that age related prevalence is constant over time. Assuming constant costs per patient, the economic burden will increase in line with our prevalence forecasts. Given that many sufferers, especially males, do not currently seek treatment, the future cost burden may also have been underestimated.