OBJECTIVES: To compare health care costs and utilizations between patients with an overactive bladder (OAB) who were adherent to OAB medication versus those who were not. METHODS: Adult patients with at least two OAB diagnoses and two consecutive OAB prescriptions (tolterodine tartrate, oxybutynin chloride/transdermal, trospium chloride, solifenacin succinate, darifenacin hydrobromide) between July 1, 2007-December 31, 2010 were selected from the MarketScan Commercial and Medicare Supplemental Claims Database. Continuous eligibility for 6 months pre- and 12 months post-index date (first OAB prescription date), and no prior use of OAB medications during the 6-month baseline were required. Adherent (proportion of days covered [PDC] to medication ≥0.8) and non-adherent (PDC<0.8) cohorts were defined. Follow-up health care costs and utilizations were compared between the cohorts. Propensity score matching was used to control baseline differences in age, gender, region, comorbidities, costs and utilizations. RESULTS: A total of 45,856 patients were identified (adherent: N=11,851; non-adherent: N=34,005). Adherent patients were older (65.40 vs. 62.50, p<0.0001), more likely to be male (34.01% vs. 30.59%, p<0.0001), and had higher Charlson Comorbidity Index scores (1.34 vs. 1.24, p<0.0001). During 1-year follow-up, adherent patients had lower inpatient (17.00% vs. 21.32%) and emergency room (ER) visit rates (27.12% vs. 32.21%), lower medical costs ($22,608 vs. $26,000), but higher pharmacy costs ($12,382 vs. $7,526) than non-adherent patients (all p-values<0.0001). After matching, 11,850 patients from each cohort were further analyzed. Adjusted outcomes revealed that adherent patients had lower inpatient (17.00% vs. 23.99%) and ER visit rates (27.11% vs. 34.24%), translating to lower inpatient costs ($6,453 vs. $9,187, p<0.0001). Higher pharmacy costs for adherent patients (all-cause: $12,374 vs. $9,011; OAB-related: $2,238 vs. $945, all p<0.0001) were offset by lower medical costs (all-cause: $22,553 vs. $27,985; OAB-related: $732 vs. $1,289, all p<0.0001). CONCLUSIONS: Higher adherence with OAB medications was associated with fewer inpatient and ER visits, higher pharmacy costs, but significant lower medical and total costs.