OBJECTIVES: Abiraterone acetate is a CYP17 inhibitor indicated for treatment of patients with metastatic castration-resistant PC in combination with prednisone. The recommended dose is 1000mg (four 250mg tablets) administered once daily in combination with prednisone 5mg administered twice daily. This study evaluated U.S. real world abiraterone acetate utilization patterns in PC patients during the first year of commercial abiraterone acetate availability. METHODS: Prometis administrative claims data (6/2009 - 5/2012) were used to identify patients with ≥1 PC diagnosis (ICD-9 185.xx, V10.46) and ≥6 months of claims activity before their first abiraterone acetate prescription (index date). Population characteristics, number of abiraterone acetate fills, daily dose, refill interval, and Medication Possession Ratio (MPR) were summarized with descriptive statistics (n, %, mean±SD, median). RESULTS: A total of 1,545 PC patients with ≥1 abiraterone acetate prescription and prerequisite claims activity were identified.  The majority were ≥65 years of age; 82% were treated by an oncologist; 58% had abiraterone acetate claims covered by commercial insurance and 38% by Medicare; 49% had ≥ 6 months of post-index clinical activity.  The median abiraterone acetate dose was 1,000 mg (mean±SD =995.6±48.6 mg). The median refill interval was 29.8 days between dispensings (mean±SD=34.3±16.4 days). MPR was 0.96±0.10.  CONCLUSIONS: This retrospective study of early abiraterone acetate utilization in a large cohort of PC patients showed median abiraterone acetate dosing and refill intervals consistent with the product label.