Studies on seasonal prevalence and population density of Anopheles sinensis were carried out in the Munsan area at the northwestern part of Kyonggi province in 1994~1997. A total of 18 species in 5 genera were collected using New Jersey light traps. In addition, weekly human biting collections were performed at Taesongdong, close to the DMZ area from 15 May to 10 September, 1997. A total of 17 species in 5 genera were collected in the biting collections. Anopheles sinensis showed two peaks of biting activity at 22:00~24:00 and at 02:00~04:00 in July. In August the times shifted to a different biphasic pattern with peaks at 20:00~22:00 and at 02:00~06:00. In September there was only one peak in biting activity at 19:00~21:00.