On the gel filtration, using Sepharose 2B, of the supernatant from ultracentrifugation hf homogenized chorioallantoic membrane of infectious bronchitis virus infected chicken embryos, a fraction, which was not detected in the chromatographic pattern of similar material from normal chicken embryos, bearing hemagglutinating activity first appeared, and a peak of absorbancy at 280mμ in both sides of which hemagglutinating activity of low level was detected, later appeared.The activity of the above two kinds of hemagglutinin isolated from infected chorioallantoic membrane was inhibited with the fraction which eluted later.The hemagglutinin which first eluted in gel filtralion of infected chorioallantoic membrane, was composed of lipid of 76.7%, protein of 17.9%, carbohydrate of 5.3%, and nucleic acids were not almost contained.The activity of the above hemagglutinin was held at 4°C for 72 hours. At 25°C a half level of that activity was maintained for eight hours and lost after 72 hours. At 37°C or 56°C it was lost almost after 12 hours.The optimal pH range in activity of the above hemagglutinin was from 7.0 to 8.0.The component, responsible for hemagglutination, in ether extract from this hemagglutinin was thought to be any member of sterol group (other than cholesterol).