The author made experiments on hypersensitiveness of the skin with azoprotein, and obtained the following results. 1) Positive effects can be observed on the skin of rabbits or guinea-pigs that have been sensitized with azoproteins actively or passively when injected with the same antigens. 2) Hypersensitiveness of the skin is most positive in 7 hours after the injection in case of azoproteins as the passive sensitization. 3) The positivity of skin reaction is proportional to the antibody value in the blood on experiments made under the same and constant conditions. 4) The antigen stays longer in the skins of sensitized animals than of not sensitized. 5) The stronger the sensitization is, the longar and the more the antigen stays in the skins. 6) The diffusion of the antigen from the skin is slow at the time of the strongest skin reaction, that is, in 3-12 hours after the iniection. 7) Compared animals sensitized actively with those sensitized passively, the former have more positive skin reaction, and its local antigens stay longer.