The population trends of chironomid larvae in Lake Monroe in central Florida and the occurrence of adult midges around residences and businesses along the southern shore of the lake in Seminole County were studied from January 1979 to July 1984. Glyptotendipes paripes Edwards and Chironomus crassicaudatus Malloch were the predominant species as larvae and as adults. Larval densities (Ekman dredge samples) of G. paripes and C. crassicaudatus fluctuated between <1 and >6000 and <1 and ca. 1800/m^2, respectively. The density of total midge larvae was the highest (ca. 7000/m^2) in August 1979 and the lowest (100/m^2) in July 1982. There was a decline of 80% of total larvae in the lake in 1983 as compared to 1979. In New Jersey light trap collections, G. paripes was the predominant species (>70%) in 1980. It was outnumbered by C. crassicaudatus (60% of all midges) in 1981 and 1982. In 1983, populations of G. paripes returned to 63% while C. crassicaudatus declined to 6% of the total adults. Peaks of adult emergence usually occurred from May to November when in some catches >500,000 adult midges were taken in a trap in 1 night. There was a considerable reduction (up to 93%) of adult midges in the study area from 1981 to 1984. This reduction was primarily due to the lower number of G. paripes and C. crassicaudatus.