Species of flies collected with the putrefied squid baits in Mt. Gumo, Gumi, Korea from March to November, 1983, included 5 families,23 genera and 39 species. Even (bough Phaenicia sericata, Musca donestica and Muscina stabulans constitituted above 50% of the total catches in residential area and farmhouses, the percentaae of these three species was found to be 3% by the current investigation. The number of flies collected was 46,831 in total, of which 31,2% was male and 68.8% female. Hydrotaea dentipes, Calliphora lata and Lucilia caesar, the three predominant species in each trap, constituted 65% of the total collections. The higher the altitude at which the traps were placed, the more Hydrotaea dentipes, Calliphora lata and Lucilia caesar were collected; in contrast, Phaenicia sericata, Chrysomyia pinguis and Ophyra leucostoma were predominant at the lower altitude where trap 1 was placed. As to the seasonal prevalence of the flies collected in Mt. Gumo, the peak appeared twice on fay 11 and September 13 ; the number of peaks was fewer and the prevalence curve was smoother than in 4he low land. The size of 4he catches, appeared to closely related to the temperature on the day of collection and the sudden fall of the temperature affected the traps placed at the higher altitude to the greater extent than (hose at the lower altitude. As to the seasonal prevalence noted at each trap placed at different altitude, traps 2 and 3 located in alpine area showed simitar prevalence curves Calliphora lata, Aldrichina grahami and Hydrotaea dentipes showed the highest peak of prevalence in May and June, and conspicuously decreased in July and August, while Boettcherisca perrgrina, Lucilia caesar and Muscina angustifrons were continually collected until July and August. Chrysomyia pinguis rarely occurred from March to June and showed the unique seasonal prevalence with two distinct peaks in early September and mid-October Phaenicia sericata scarcely occurred in traps 2 and 3, and showed the seasonal prevalence only in trap 1.