I study the impact of expanding the 340B Drug Pricing Program to include Critical Access Hospitals (CAH) on Medicare Part B drug utilization and spending. The 340B program entitles certain hospitals and clinics to discounts on most outpatient drugs. In 2010, the Affordable Care Act expanded 340B eligibility to CAHs – small rural hospitals that receive cost-based reimbursement from Medicare. Exploiting variation in the predicted exposure to the 340B expansion in a difference-in-differences method, I find that the 340B expansion reduced Part B drug spending but did not affect Part B drug utilization. This finding contrasts with existing evidence about 340B’s impact on hospitals but is consistent with the prediction that cost-based reimbursement dampens the incentives created by the 340B discounts. I also find suggestive evidence that CAHs passed the cost savings from 340B on to patients. These results add new perspectives to the ongoing debate over 340B.