Current information is reviewed from 26 cases of human infection by DF-2, a fastidious gram-negative rod. These infections are typically associated with dog contact or dog bites. Underlying diseases or prior splenectomy are predisposing factors for severe infection with a potentially fatal outcome. The methods for isolating and identifying the microorganism are given. Long, thin, slowly growing, oxidase-positive, catalase-positive gram-negative rods that do not grow on MacConkey agar should suggest DF-2. Although testing of antimicrobial susceptibility is problematic, DF-2 has been found to be resistant to aminoglycosides. The drug of choice is penicillin.