A survey was carried out during 1998-1999 to determine the distribution and seasonal abundance ofAn. minimus Theobald in Ishigaki Island, Ryukyu Archipelago, Japan, Larvae and pupae ofAn, minimtcs were collected in 33 of48 streams in 1998, and 38 of 56 streams in 1999. Immatures ofAn. minimus were found in almost all the surveyed streams except those in urban areas, fast flowing streams and polluted streams. The abundance of immatures in Fanan and Nishihama Streams, where a lot of the immatures was collected, showed seasonal variation which was positively correlated with water temperature and rainfa11. Few immatures were collected during winter season (December to February). As the temperature started to rise in March, the population increased and the density became high from May to August, and October to November, 1999. In Arakawa Stream near urban area, unlike Fanan and Nishihama Streams, the population of An. minimus immatures became biggest from March to April. By light trap method, more than 30 An. minimus adults per night were collected from March to November except MaM and the highest number was 228 in July and 321 per niglit in November, 1999, near Nishihama Stream. INTRODUCTION Until 1962, Ishigaki Island and ether islands including Iriomote lsland of Yaeyama, Ryukyu Archipelago were endemic fbr malaria which was mainly transmitted by Anopheles minimus Theobald, The epidemic of malaria especially occurred afier World War II in 1945 when 53.8% of the total population in the islands were infected (WHO, 1966; Tleruya, 1975; Eshita, 1982). Malaria was eradicated in these is]ands after initiation of eradication prograrn fbcusing on, among others, the control of yector mosquitoes using DDT, The program,