An attempt was made to serological classify the infectious canine hepatitis (ICH) virus using 14 strains isolated from U.S.A. and Japan. Human, guinea-pig and chicken erythrocytes were agglutinated by all strains tested and no differences in hemagglutination characteristics were demonstrated. No or spontaneous agglutinations were observed with red blood cells from dog, mouse, rabbit and hamster. Conventional cross-hemagglutination inhibition and -serum neutralization tests were conducted and the "γ" values of the antigenic relationships were calculated by the formula of ARCHETTI & HORSFALL (1950). The lowest "γ" values found were 0.84 and 0.78 respectively suggesting a fairly close antigenic relationship between the strains tested. It appeared from the 14 strains studied that the ICH virus, consists of only one serotype
