Canine brucellosis is a worldwide disease of dogs characterized prinicpally by abortions in females and epididymitis and infertility in males. It originally was observed in the USA, but recently it has been discovered in Japan, Mexico, Peru, Germany and, possibly, in Brazil. It affects dogs of all breeds and has been diagnosed in breeding kennels and in stray dogs. Several human cases have occurred, with 6 being accidental infections by laboratory personnel. B. canis, like B. ovis, is naturally mucoid, lacking "S" antigens. Serological tests therefore are not appropriate to classification. On the basis of manometric technics, B. canis is similar to B. suis; nevertheless the host range excludes swine. Agreement on its taxonomic status is not universal, although it has been provisionally accepted by the Subcommittee on Taxonomy of Brucella as a new species. A brief review of salient characteristics of B. canis was presented, however the principal discussion focused on recently observed aspects of the immunopathogenesis of male infertility and reported the development of a rapid slide agglutination test, using as antigen a concentrated and stained (Rose Bengal dye) suspension of B. ovis.