OBJECTIVES: This study estimates the costs of AIs sunitinib, sorafenib, and bevacizumab using economic modeling based on recorded healthcare resource utilization from medical charts. METHODS: Non-trial mRCC patients, ≥18 years, who received ≥1 prescription for sunitinib (n=57) or sorafenib (n=62) or ≥1 intravenous administration of bevacizumab (n=25) after Janaury 1, 2005 as first-line AI were included.  Total per-patient-per-month (PPPM) costs (US$2008) included costs of AI drugs, office visits, procedures, and treatment of adverse events (AE) resulting in hospitalization or emergency room (ER) visits.  AI drug costs were estimated by applying Average Wholesale Price to each patient’s observed treatment course (initial dose, dose changes, and treatment duration).  Office visit and procedure costs were based on US private insurance reimbursement.  Hospitalization costs were based on HCUP National Inpatient Sample average charges associated with AE diagnosis; cost-to-charge ratios were applied.  ER visit costs were based on national averages from Medical Expenditure Panel Survey. RESULTS: Median treatment duration was10.5 months (sunitinib), 8.1 months (sorafenib), and 7.9 months (bevacizumab).  Total healthcare costs PPPM (mean±SD) were $7,945±2,993 (sunitinib), $6,990±3,073 (sorafenib), and $15,189±1,859 (bevacizumab).  AI drug costs comprised 71% (sunitinib), 75% (sorafenib), and 90% (bevacizumab) of the total PPPM cost.  All-grade AE costs PPPM were $729±SD (sunitinib), $636±SD (sorafenib), and $291±SD (bevacizumab).  Given the median treatment durations, the total cost over the course of first-line AI treatment is estimated at $83,422 (sunitinib), $56,622 (sorafenib), and $119,996 (bevacizumab), including AE treatment cost of $7,656 (sunitinib), $5,149 (sorafenib), and $2,297 (bevacizumab).  CONCLUSIONS: AI drug cost was a major contributor to the total healthcare PPPM cost in patients with mRCC, especially for patients receiving bevacizumab.  This retrospective study is limited by small sample sizes.  Future studies examining comparative cost-effectiveness of these AIs are warranted to evaluate clinical and economic effects of these AIs.