To forge a path to progress in improving health care and reducing costs, payers, practitioners, and policymakers increasingly agree that we need to strengthen primary care. Mathematica’s seasoned experts continue to lead research and provide evidence on primary care transformation to support a national shift in care delivery. Recently, Mathematica completed the first annual report of its independent evaluation of Comprehensive Primary Care Plus (CPC+), the largest and most ambitious primary care and delivery reform ever tested in the United States.