Chironomid larval densities in two saltwater lakes, East and West Lake, surrounding the city of Orbetello, in west-central Italy, were assessed in the summer of 1982. Observations were made on adult midge swarms in the area surrounding the lakes. Chlorpyrifos, temephos, fenthion, malathion and Bactimos (Bacillus thuringiensis serotype H-14) were evaluated in the laboratory against field-collected larvae. Only Chironomus salinarius was recovered from the lakes with densities ranging from 178-25,775 and 89-33,330/m2 in East Lake and West Lake, respectively. Larval populations within 1km of shore along the city were significantly higher than in the remaining area of each lake. Swarms of adult C. salinarius were the densest at night around fluorescent and incandescent white lights as compared to those lights of blue, green and red colors. Larvae of C. salinarius were most susceptible to chlorpyrifos (LC90 =0.0032 ppm) and least to fenthion (LC90=0.091 ppm). Bactimos was relatively ineffective (LC90 =5.07 ppm). Treatment of a partial area of each lake (within 1 km of Orbetello) with chlorpyrifos or temephos will probably produce a significant reduction of midge larvae.