Project Summary As a prominent leader in the nationwide shift towards value-based payment, Medicare has implemented large fee-for-service population- and episode-based alternative payment models (APMs) that hold organizations financially accountable for the quality and costs of care. However, these APMs are not designed to protect access or outcomes for racial/ethnic minorities and individuals with low socioeconomic status. These vulnerable groups already face significant surgical disparities compared to other individuals. These disparities could worsen further under both APM types if participating providers engage in patient selection that reduces vulnerable patients’ access to surgical procedures or changes their care after participating. Because policymakers must make critical decisions about how to use different APMs to catalyze nationwide reform, insight about how population- and episode-based APMs affect surgical disparities for vulnerable patients can help policymakers determine how to best design, refine, implement policy adjustments, and scale up different models to safeguard the care of vulnerable patients. This study examines how prominent Medicare fee-for- service population- and episode-based APMs that are highly relevant to surgical care affect disparities in surgical access and outcomes for vulnerable patients, across insurance coverage type, and whether effects vary by providers’ financial attributes related to APM incentives. We hypothesize that APM participation will be associated with widened disparities in surgical access and outcomes (quality, utilization, and cost) for vulnerable vs. non-vulnerable patients after providers begin participating in APMs. We also hypothesize that the impact on surgical disparities will vary by providers’ financial attributes – experience with financial risk and payer mix – related to APM incentives.