Objective: Traditional epidemiologic studies of interstitial cystitis (IC) have focused on diagnosed cases alone while many patients who appear to have IC have been eliminated due to strict diagnostic criteria. An association between positive potassium sensitivity test (PST), epithelial permeability dysfunction (EPD) and painful bladder syndrome/IC (PBS/IC) has been reported but limited attention has been given to these relationships in the epidemiologic area. This study was designed to seek further evidence of potassium sensitivity and therefore bladder EPD in a fixed group of Turkish women. Methods: All female workers of the two textile factories were evaluated for PBS/IC-specific symptoms by using the Pelvic Pain and Urgency/Frequency (PUF) scale and then all were asked to volunteer for PST and further clinical evaluation. Subjects who volunteered for PST were separated into two groups: group 1 consisted of subjects who had a PUF score of ≧7 and group 2 (control group) consisted of subjects who had a PUF score of ≤6. Results: A total of 80 volunteered for PST, 58 were in group 1 and 22 were in group 2. The rate of positive PST was 86.2 and 9.1% in group 1 and 2, respectively (p < 0.05). We estimated that the prevalence of bladder EPD would have been 32.80% (145/442) in a fixed female population in our region when considering the rate of positive PST in group 1. Conclusion: Our data provide further support for the high prevalence of an increased potassium sensitivity which is a reliable indicator of EPD in a fixed female population.