A total of 945 adult dogs, 572 stray and 373 nonstray ones, collected fromTokyo area, were examined for Brucella canis infection and 27 (2.9%) cases were found tohave high titered agglutinin and/or the organism. With the exception of a colony of non-stray dogs showing a positive rate of 12.77., no significant difference in positivity rates wasseen between stray and nonstray dogs. Bacteremia was detected in 12 cases out of 459cases examined, and 9 positive cases had high titered antibodies. In 9 out of 11 autopsiedcases having high levels of agglutinin or positive blood culture, the organism was isolatedfrom the spleen, Nymph nodes, liver and male genital organs with high frequency. Amongthese cases carrying the organism, high titered specific agglutinins were usually resistantto 2-mercaptoethanol treatment, while low titered agglutinins, probably nonspecific, weresensxtuve.