During 1970-1972 haemobartonellosis occurred in research canines at 2 widely separated institutions. Clinical anemia occurred in a splenectomized dog at a Maryland [USA] facility, and subsequent screening disclosed an infection rate of 65% in a group of 20 splenectomized subjects. Treatment was successful, and the animals were used in research. A research institution in Texas [USA] encountered a number of dogs with fever (to 106.degree. F) and eosinophilia (to 42%) following minor surgery. Blood from affected animals was injected i.v. into splenectomized dogs, and 3 of 6 recipients developed haemobartonellosis. Further study was conducted, with some success, to establish a relationship between fever and eosinophila and H. canis infection in nonsplenectomized subjects. Haemobartonellosis is apparently a widespread, latent disease of dogs and significant potential exists for the infection to adversely affect research results.