Summary A method of producing a bacteremia consistently in dogs by injecting intravenously one billion Staphylococcus aureus organisms is described. Cultures used were fresh. Cells were suspended in sterile saline to eliminate toxic products of metabolism. Thirty dog experiments were carried out. These dogs were divided into three equal groups. All groups were inoculated with Staphylococcus aureus organisms, the phage type differing for each group. The most immediate and consistent results were obtained in dogs inoculated with Staphylococcus aureus, phage type 80/81. This method has been found to be an effective means of studying the effects of circulating organisms on vascular prostheses. The mortality rate is not prohibitive.