1) Yoron is the farthest southern island of the Osima archipelago, only 20 miles north from Okinawa. After admission of 60 lepers in Keiaien from Yoron in May 1938, the whole Yoron villagers wished to be examined.2) 7.470 among 7954 inhabitants were examined in August 1938 by the author and 17 leprous patients newly were found. Total number of lepers, therefor, is 78.3) While the census in 1935 numbered 15, 193 lepers in Japan, there were only 24 on the list in this island, t. i. 1/3.3 of 78. In 1937, the author examined Kikai island and the number of lepers was 1.8 times of census number in 1935.4) Lepers are seen in every part of the island, equally prevalent as seen on the map 1.5) 78 patients are consisted of 46 male and 32 female, t. i. 1.4: 1. But as females in this island is 20% more than males, the male leper proportion becomes more.6) Lepromatous form are 23.1 %, less than 32.4% in Kikai. Lepromatous type in Japan is estimated to be 30% or so of all lepers.7) The modus of infection are classified into three; from relatives 40%, from neighbours 16.7% and without any infecting chance 43.3%. The nearer is the infecting source, the earlier is the onset age; 19.0, 21.8, 22.1 average ages respectively.8) Filaria, intestinal parasites; ascaris and ankylostoma and trachoma are very prevalent, partly due to the lack of water.9) As the island is isolated, measles epidemy comes in every 5 or 10 years. So only 24% of all the patients had been attacked with it till 5 years old, while in other part of Japan 40 or 50% ace used to fall in first five years.10) Tuberculosis is very rare. Positive Mantoux reaction is only 6% among Yoron lepers admitted in.11) Age distribution curve shifts to left just as Okinawa curve, and just contrary to the right shifting curve of lepers in Kagoshima proper as seen on plate 2. Average ages of patients are 37.2 in Yoron, 38.2 in Okinawa and 47.0 in Kagoshima proper. In Yoron, it is 42.5 at Tyabana, where there are many old neural patients, and 32, 6 at Higasi, where there are some young lepromatous patients.12) Neither leprous blind, nor leprotic alopecia in high grade were found in Yoron and this certifies the author's climate theory.13) The newly found patients are classified into, two; one group is macular or early lepromatous form, and the other is old slight neural form.14) The duration of the disease are very important to investigate local epidemiology. For example, the average duration in Norway is 45 years, and at Ranikhatanga village in India is 4.1, while at Tyabana in Yoron 25.9 and 9.1 at Higasi, Nisi and Gusuku.15) Additionally the number of patients, whose duration of the disease are under 5 years, is very important from epidemiological stand point. In Norway, no patient is under five years duration, while in Ranikhatanga 70% of all are under 5 years duration. In Yoron, this percentage is 0 at Tyabana, and 43% at Higasi.16) Notwithstanding the fact that no propaganda had ever been taken place in Yoron, 60 patients were sent to Keiaien and total inhabitants were examined this time. Village master, Mr. Tanaka announced recently that this examination of all the inhabitants should be held every year for 10 years and sending new patients to Keiaien, leprosy free Island should be completed.Though Yoron is the remotest place from civilization in Japan, this attitude for leprosy problem is the best model in Japan.(Abstracted by the author)