This issue of Physician Assistant Clinics, guest edited by Drs. Vincent Morelli, Roger Zoorob, and Joel J. Heidelbaugh, is devoted to Primary Care of the Medically Underserved. Articles in this issue include Primary Care Issues in Rural Populations; Primary Care Issues in Inner City America and Internationally; Medical Care for Undocumented Immigrants: National and International Issues; Pediatric and Adolescent Issues in Underserved Populations; Women's Select Health Issues in Underserved Populations; Medical Care of the Homeless: An American and International Issue; Occupational Health and Sleep Issues in Underserved Populations; Infectious Disease Issues in Underserved Populations; Psychological Issues in Medically Underserved Patients; Substance Use Issues Among the Underserved: United States and International Perspectives; Diet and Obesity Issues in the Underserved; Exercise and Sports Medicine Issues in Underserved Populations; Environmental Justice and Underserved Communities; Climate Change and Underserved Communities; Geriatric Care Issues - An American and an International Perspective; Cardiovascular Health Disparities in Underserved Populations; Cancer in the Medically Underserved Population; and International Comparisons in Underserved Health - Issues, Policies, Needs and Projections. CME credits are also available to subscribers of this series.