Alves, A.L.; Botteon, R.C.C.M.; Brito, S.N.; Botteon, P.T.L. & Jesus, V.L.T. [Occurence of canine brucelosis in Seropedica City - Rio de Janeiro.] Ocorrencia de brucelose canina no Municipio de Seropedica - Rio de Janeiro. Revista Brasileira de Medicina Veterinaria 30(3):152-156, 2008. Departamento de Medicina e Cirurgia Veterinaria, Instituto de veterinaria, Universidade Federal Rural do Rio de Janeiro, BR 465, km 07, Seropedica, RJ 23890-000, Brasil. E-mail: rbotteon@ufrrj.br In a period of two years, were collected samples of blood of 134 dogs from one of the boroughs Jardim Maracana, Coqueiral / Boa Esperanca and Campus of the University Rural, situated in the Municipatity of Seropedica, Rio de Janeiro State. This samples was submitted to the test of imunodifusion in gel of agarose using antigen of the B. ovis and controls serum from the Institute of Technology of Parana (TECPAR). The tests was modified by the use of Agar Noble and saline solution 0,85% (Myers & Sinuk, 1970), adapted for diagnosis of infection of the B. canis (Alton et al., 1976), proceeding it analysis statistics for the accurate test of Fisher to livel of significance of 95%. In 134 serums analyzed, 58,2% was positive (78/134), don't have statistical difference with the variable sex, age, race and acess to the street. In all the boroughs the prevalence of positive serum from B. canis was greater that 50%. The seroprevalence of B. canis was major in the boroughs Coqueiral/Boa Esperanca and Jardim Maracana them in the University Rural (p<0,05). The owners of the 10 positive dogs had told alterations as abortions, stillborn and neonatal death, compatible manifestations with the disease. The others were asymptomatic.