The peritoneal exudate containing a large amount of rickettsiae were obtained by intraperitoneal inoculation of Rickettsia tsutsugamushi into the guinea-pigs previously injected with chlorpromazine. The antigenic substance of thus obtained peritoneal exudate was absorbed on bentonite and pine-resin particles, and was used as the agglutination antigen. The flocculation antigen was prepared from the lung of the mice intranasally inoculated with rickettsiae. By means of the seroreaction with the use of these two sorts of antigens, the author studied the influence of the difference of the amount of rickettsiae as well as the sites of inoculation on the immunity. Intracutaneous, subcutaneous, intracerebral, intraperitoneal and intranasal routes were chosen as the sites of inoculation of living rickettsiae. The intracutaneous inoculation produced the flocculation antibodies in the largest amount, the intracerebral and subcutaneous ones the nest, and they were followed by the intraperitoneal and intranasal ones. In the case of inoculation by the routes other than nose, the antibody titer rised with the lapse of time after inoculation. When inoculated by the same route, within the range of a certain amount of rickettsiae, the difference of amount gave no influence on the production of antibodies. The agglutination reaction with the use of the particle-absorbed antigen was not feasible because of its non-special reaction.