OBJECTIVE: To evaluate the impact of patient selection criteria on baseline characteristics and selected outcomes in a cohort of patients with overactive bladder (OAB). METHODS: Newly diagnosed OAB patients were identified from a medical and pharmacy claims database including more than 30 geographically diverse managed care plans. Two patient cohorts were compared for baseline characteristics, treatment status, and incidence of selected urologic conditions following diagnosis. The first group required only one claim with an OAB diagnosis (DX1); the second required a confirmatory claim (DX2). RESULTS: A total of 113,061 DX1 and 39,863 DX2 patients were identified. Mean ages for DX1 men and women were 60 y and 52 y, respectively; mean ages for DX2 men and women were 57 y and 49 y, respectively. In total, 28% of DX2 patients and 10% of DX1 patients received pharmacologic treatment. Of those untreated, 49% were men in DX2 group and 41% in DX1 group. In total, 26% of DX2 women and 20% of DX1 women had baseline urologic infections, and 17% of DX2 women and 12% of DX1 women had baseline urologic disorders. A total of 11% of DX2 men and 9% of DX1 men had baseline urologic infections, and 28% of DX2 men and 21% of DX1 men had baseline benign prostatic hyperplasia. In DX2 patients, the adjusted odds of urinary tract infection was 0.77 (95% CI, 0.73–0.80); in DX1 patients, the same estimate was 1.19 (95% CI, 1.14–1.24). CONCLUSIONS: Patients with one OAB diagnostic claim differed in demographic and clinical characteristics from those with a confirmatory claim. Furthermore, differences in percentages of patients receiving OAB treatment may suggest that health-seeking behaviors differ among patients with one and two diagnostic claims. These data support the use of a confirmatory diagnostic claim in some studies of OAB.