ABSTRACT. Barbosa J.D., Bomjardim H.dosA., Lima D.H.daS., Reis A.dosS.B., Barboza F.B., Albernaz T.T., Oliveira C.M.C., Fonseca A.H., Nicolino R.R. & da Silva J.B. Detection of brucellosis in water buffaloes for exportation in northern and northeastern of Brazil. [Detecção de brucelose em búfalos d’agua para exportação no norte e nordeste do Brasil}. Revista Brasileira de Medicina Veterinária, 38(supl. 3): 129-135, 2016. Laboratório de Doenças Parasitárias, Departamento de Epidemiologia e Saúde Pública, Instituto de Veterinária, Universidade Federal Rural de Rio de Janeiro, BR 465, Km 7 Seropédica, RJ 23890-000, Brazil. E-mail: email@example.com The prevalence of brucellosis in buffaloes was evaluated by the Buffered Acidified Plate Antigen (BAPA) in 5.163 water buffaloes from Maranhão state, Pará state and Marajó Island, Brazil. The detection of buffaloes positive for brucellosis by BAPA was 7.37% in Marajó Island, 8.45% in Pará state and 29.86% in Maranhão state. The locations with the highest prevalences were Santa Cruz do Arari, in Marajó Island (12.50%); Ipixuna, in Pará state (30.25%); and Santa Inês, in Maranhão state (34.76%). After the confirmatory test (Complement Fixation Test), only 7 animals remained positive in Marajó Island, and 22 remained positive in the state of Pará. None of the 66 animals that reacted positively in the BAPA test in Maranhão reacted positively in the CF. The high prevalence of B. abortus that was observed in animals, especially in the state of Maranhão, is worrisome for the health system for the control and eradication of bovine brucellosis.