It has been known that there are more than 50 species of mosquitoes in Korea but little study was done on distribution of summer mosquitoes species in Seoul. The author collected and investigated the species and seasonal distribution of mosquitoes in Seoul from 1967 to 1972. 1) The most abundant species of summer mosquitoe was A. vexans nipponii, $30{sim}70%$ of total mosquito population. 2) The next abundant species was C. pipiens but there was wide frequencies according to different years. 3) C. tritaeniorhynchus, the vector of Japanese encephalities, was third in order, possesed about 9% of total mosquitoe population every year and reached peak in August and September. 4) It was found that there ware 7 species of mosquitoes commonly in Seoul City.