The author studied on the pathogenicity and complement-fixing antigenicity of the peritoneal exudate of guinea-pigs previously injected with chlorpromazine and then inoculated with Tanizawa strain of Rickettsia tsutsugamushi. Both of the exudates with and without visible rickettsiae were used as the experimental materials. The results were as follows: 1) whether contained visible rickettsiae or not, the exudates showing the specific inflammatory pictures had no significant difference in their pathogenicity. 2) The exudates showing the specific inflammatory pictures had the same titer of complement-fixing antigenicity, regardless of appearance or non-appearance of visible rickettsiae. 3) Whether contained visible rickettsiae or not, the exudates showing the specific inflammatory pictures did not show any significant difference of antigenicity against the rabbit immunesera immunized by subcutaneous, intraperitoneal or intrascrotal inoculation of exudates. Of all the inoculation sites tested, intraperitoneal one produced the antisera of the highest titer. 4) In short, regardless of the presence or absence of visible rickettsiae, the peritoneal exudates showing the specific inflammatory pictures had no noticeable difference in their pathogenicity and complement-fixing antigenicity. The cellular pictures of peritoneal exudates are the specific reaction figures to multiplication of rickettsiae, and appearance of rickettsiae depends on the growing stadium of ricketsiae and, moreover, depends on the technic of stain.