We evaluated whether primary care practices in the Medicare Multi-Payer Advanced Primary Care Practice (MAPCP) Demonstration improved the quality of care and patient outcomes for beneficiaries.For our quantitative analyses, we employed a pre-post study design with a comparison group using enrollment data, Medicare fee-for-service claims data, and Medicaid managed care and fee-for-service claims data, covering the period 2 to 4 years before Medicare joined the state patient-centered medical home initiatives through December 2014. We used difference-in-differences (DID) regression analysis to compare quality and outcomes in the period before and after the demonstration began.We examined the extent to which MAPCP and comparison group beneficiaries received up to 11 process and preventive care measures, as well as 4 measures of potentially avoidable hospitalizations to assess patient outcomes.Analyses of Medicare and Medicaid data did not consistently reflect the positive impacts intended by the demonstration. Our descriptive and DID analysis found an inconsistent pattern among the process-of-care results, and there were some significant unfavorable associations between participation in MAPCP and avoidable hospitalizations.Our analyses showed few statistically significant, favorable impacts on quality metrics among Medicare or Medicaid beneficiaries receiving care from MAPCP practices.