Summary Under specific conditions of temperature and of pH the virus of infectious canine hepatitis enters into a reversible association with fowl erythrocytes. By adsorption with these cells both the hemagglutinin and infective particle could be removed from tissue culture fluids containing ICH virus without appreciably reducing their ability to act as efficient complement fixing antigens. Variations both in susceptibility to heat and to precipitability with methanol have also suggested a closer association to exist between hemagglutinin and the virus particle than with the complement fixing antigen. A limited number of observations upon the growth of ICH virus in dog kidney epithelial cell monolayer cultures in relationship to the production of hemagglutinin and complement fixing antigen have been recorded.