Five MRC sites cover 7 Local Government Administrative Divisions in The Gambia. A further field site is situated in Caio, Guinea Bissau.

MRC Fajara (Kombo St Mary Division). The main base is situated on the coast near the capital Banjul. Features include laboratories, a hospital, computer centre, offices, workshops and residential accommodation.
MRC Keneba (Lower River Division). Main site for field based nutrition studies
MRC Wali Kunda (Central River Division) Small site for entomological studies.
MRC Basse (Upper River Division) Site of Pneumococcal Vaccine Trial (concluded in 2005). Current studies include PATH funded Meningitis Vaccine Project.
Caio (Guinea Bissau). HIV epidemiology studies have been conducted there since 1986. Caio officially became an MRC field site in 2006.

The unit also operates from Sukuta Health Centre and Sibanor Health Centre in partnership with the Department of State for Health and Social Welfare.