Dr. Greenfield is one of the country's most eminent and experienced health services researchers and policy experts.  He serves as the Executive Co-Director of the Health Policy Research Institute at the University of California, Irvine (UCI) and is a Donald Bren Professor of Medicine. He is an alumnus of Harvard College and graduated from the University of Cincinnati College of Medicine (in the shadow of HUC). He completed his Internal Medicine training at Harvard Medical School, and has served as faculty for the University of California, Los Angeles (UCLA), Tufts University School of Medicine, and the Harvard School of Public Health.  With his wife and colleague, Dr. Sherrie Kaplan (also a member of SHM), he has produced major policy findings resulting in over 35,000 citations to papers in which he has been involved.  He and his colleagues have opened at least 3 new fields: nurse practitioners, outcomes research, and patient participation in medical care.

He was president for the Society of General Internal Medicine and was appointed chair or co-chair for 4 National Academy of Sciences/Institute of Medicine (IOM) committees. He directed major reports such as: Guidance for the National Healthcare Disparities report; Cancer Survivors: Lost in Translation; Initial Priorities for Comparative Effectiveness Research; and Clinical Practice Guidelines We Can Trust. He is a current member of the California Medi-Cal Performance Advisory Committee for the Medicaid program.  He is also currently Principal Investigator of a study to compare treatments for prostate cancer, including genetic factors, so that patients can optimize their treatment choices based on their own needs and preferences.