Incidence of rheumatic diseases including rheumatoid arthritis falls to about 3 per cent of the whole population in Japan, but there has been no particular survey made so far in regard to rural population. With a view to grasping the situation of rheumatic diseases among rural people, we sent out a questionnaire to each medical service under the Agricultural Cooperative Association, and tried to surmise the incidence of these diseases in the locality on the basis of the number of patients treated by it. Disgnostic criteria of rheumatic diseases rested with each service. For each type of disease the rate of cases treated in each district against the total number of cases was obtained. Throughout the four year period of survey, the following trends were observed with regard to such rates:(1) Incidence of rheumatoid arthritis (RA) was higher in Kanto, Tokai and Chugoku districts, while it was lower in Hokkaido and Hokuriku-Shin-etsu districts;(2) Incidence of systemic lupus erythematosus (SLE) was higher in Chugoku and Tohoku districts, and was lower in Shikoku district;(3) Incidence of dermatomyositis (DM) was higer in Chugoku, Tohoku and Hokkaido districts, and lower in Kanto and Shikoku districts;(4) Incidence of polymyositis (PM) was higher in Tokai and Chugoku districts, while it was not reported from Hokkaido and Shikoku districts;(5) Incidence of scleroderma (PSS) was higher in Tohoku and Chugoku districts, but it was not reported from Hokkaido and Shikoku districts;(6) Incidence of periarteritis nodosa (PN) was higher in Tokai district, but was not reported from Hokkaido, Kanto and Shikoku districts;(7) Incidence of rheumatic fever (RF) was higher in Kanto district and lower in Tokai and Hokkaido districts;(8) Incidence of Behcet's syndrome (Beh), Sjogren's syndrome (SjS), Felty's syndrome (F), mixed connective tissue disease (MCTD), juvenile rheumatoid arthritis (JRA), overlap syndrome (OS) was on the whole higer in Tohoku and Chugoku districts, and lower in Tokai district.
Through this survey, we could at least gain a general view of rheumatic diseases treated in medical services under the Agricultural Cooperative Association. It became also clear that all of these diseases were on the increase. Further survey will have to be made in the near future in the light of respective diagnostic criteria.