Vulnerable populations, including low-income people, the uninsured, and disadvantaged racial and ethnic minorities, have more difficulty obtaining health care, receive worse care, and experience poorer health outcomes than other groups in the United States. To help ensure these populations have access to health care capable of meeting their particular needs, The Commonwealth Fund has created the Program on Vulnerable Populations. In a new blog post, Vulnerable Populations program officer Pamela Riley, M.D., M.P.H., and program associate Cara Dermody describe this grantmaking program and the newly renamed Mongan Commonwealth Fund Fellowship Program (formerly The Commonwealth Fund/Harvard University Fellowship in Minority Health Policy), which is designed for physicians interested in improving health care systems for vulnerable populations. The fellowship was named in memory of James J. Mongan, M.D., a member of The Commonwealth Fund's board of directors and chairman of its Commission on a High Performance Health System.