Michael S Taitel, Ying Mu, Angshuman Gooptu, Youbei Lou Health Analytics, Research & Reporting, Walgreen Co., Deerfield, IL, USA Objectives: This study evaluates a nationwide pharmacy chain’s late-to-refill (LTR) reminder program that entails local pharmacists placing reminder calls to Medicare Part D patients. Methods: We conducted a randomized controlled study among 735,218 patients who exhibited nonadherent behavior by not refilling a maintenance medication 3 days from an expected refill date. Patients were randomly assigned to an intervention group who received LTR reminder calls or to a control group. We used Walgreens pharmaceutical claims data from 2015 to estimate the impact of LTR calls on short-term and annual adherence. Results: The initial refill rate within the first 14 days of the expected refill date significantly increased in the intervention group by 22.8% (6.09 percentage points) compared to the control group (P