I have made researches on the kernel of an eruptive febrile disease which is usually seen, exceptionally in summer, at Aioi-mura, Okawa-gun, the eastern part of Kagawaken. The nature of this disease was unknown but I have succeeded in the isolation of Rickettsia from a patient, and made it clear that bacteriological natures and the Rickettsia isolated are identical with Rickettsia tsutsugamushi (orientalis). A similar disease in Tsuda-cho, Okawa-gun has been proved also to be Tsutsugamushi disease. while it can be seen in winter. This proves that there is a serious kind of Tsutsugamushi disease that develops in summer and a comparatively mild kind that develops in winter. The following shows the research I have made through clinical findings on each of the different types of tsutsugamushi disease. 1. Both Aioi-mura and Tsuda-cho are topographically located near the sea. It is usually the case that the patients houses are situated in lower land districts. 2. It develops only in summer in Aioi-mura with the duration of months from June to September. 3. It develops irrespective of age. In the block of Umayado (Aza Umayado) and Sakamoto (Aza Sakamoto) of Aioi-mura, I have found all the people, regardless of their ages, exposed in their home to the attack of the disease. 4. People of the contaminated areas are engaged in farming with fishing as their side job. Almost none of them raise pigs. This shows that pigs are not the cause of it. It is not as yet clear whether it is from the migratory birds. 5. No relation of cause and effect can be found between the occupation of the villagers snd the outbreak of the disease of the patients. 6. Clinical findings of the patients Mr. Mitani who had the disease in summer in Aioimura, and Mr. Tanizawa, in winter in Tsuda-cho are both found to be the same with those of Tsutsugamushi disease, and antibiotics especially the Terramycin is effective for it. Serums of the patients agglutinated the OXK remarkably, and assurance of the rising of the agglutination titers shows that it does not differ from the Tsutsugamushi disease. 7. The antibiotics especially the Chloromycetin and Terramycin are very effective. With these antibiotics the fever goes down. After the fever drops, it is difficult to isolate the Rickettsia from the blood. In brief, I have analyzed the clinical findings of de-velopment of "Umayado Disease", a local eruptive febrile disease, and at the same time, classified the peculiar local type of Tsutsugamushi disease according to the clinical findings into the summer type and the winter one. This leads to the fact that in a single prefecture and moreover at the places quite close to each other there can be seen a serious and a mild type of Tsutsugamushi disease in summer and winter respectively, which I think is sure to contribute to the study on the distribution and epidemic researches of Tsutsugamushi disease.