Flies and mosquitoes were collected by fly traps, light traps and sweep methods once a week over a total of 64 times in Mt. Juwang, Korea during two years from Feb. 1990 to Feb. 1992. A total number of flies collected was 47,495, with sex ratio of 47%. The fauna of the fly was found to be 55 species consisting of 11 Calliphoridae, 20 Sarcophagidae, 22 Muscidae and 2 others. Among them, although Calliphoridae accounted for 20% of the total number of fly species, constituted 78% of that of individuals collected by fly traps. The dominant species, Chrysomyia pinguis, Calliphora lata and Hydrotaca dentipes constituted 68.7% of the total individuals of flies collected in the three traps In seasonal prevalence, the peaks of flies appeared twice, in May and August in 1990, and in June and August in 1991. Although the pattern of seasonal prevalence of flies showed almost identical in each trap, the period of appearance somewhat differed according to the environments where it is installed. The result of comparition of the seasonal prevalence of the 10 predominant species among 42 species collected by fly traps, were found to exhibit a specific character. The correlation between the total number of fly individuals and that of species collected with three traps was found to be very close. The fauna of mosquitoes collected by light trap was found to be 9 species belonging to 8 Culicinae and 1 Anophelinae. The seasonal prevalences of the three dominant species, Anopheles sinensis, A migeres subalbatus and Culex tritaeniorhynchus summorosus were compared.