The result of surveillance of adult mosquitos in Ihgok-ri, Cheolma-myun, Gijang-gun, Busan located in the south-east of the Korean peninsula from 1996 to 1999 are presented. A light trap was operated twice a week from May to October each year. Average numbers of female mosquitoes per trap-night were 366.5, 751.6, 406.0 and 468.7 adults in 1996, 1997, 1998 and 1999, respectively. Total 9 species comprising 4 genera were collected. They are Aedes albopictus, Ae. vexans, Ae. togoi, Anopheles sinensis, An. sineroides, Armigeres subalbatus, Culex orientalis, Cx. tritaeniorhynchus and Cx. pipiens. An. sinensis (60.2 %) was the most abundant, followed by Cx. tritaeniorhynchus (27.1 %) and Cx. pipiens pallens (8.6%). A population density of An. sinensis in 1999 was 3.2 times lower than that in 1997. However, The density of the species in 1999 was not much different from those in 1996 and 1998. It was assumed that major factors to influence population of An. sinensis were temperature(r = 0.90) and precipitation(r = 0.74) during three summer months.