Field tests were made (1944) with an aerosol generator, developed at Columbia Univ., to determine the practicability of stable DDT-oil aerosols, dispersed from a ground vehicle, for the rapid control of adult mosquitoes over large areas. Results show aerosols can be effectively employed in the field for mosquito control operations. Aerosol treatment will kill adult Anopheles in tree holes, hollow logs, and other natural resting places. The method should prove applicable to general insect control. A dosage of 15 gallons, of 50 parts oil-50 parts water emulsion, by volume, and containing DDT equal to 10% of oil wt., per 1000 ft. of front will give effective adult control up to about one mile down wind in open country under favorable meteorological conditions, and to about 1000 ft. in forested areas. This dosage will produce practical larval control up to about 2000 ft. in open country and from 500 to 1000 ft. in forested areas. For control of adults, a 10m[mu] diam. aerosol can be used regardless of wind velocity and terrain. For larval control the particle size should be increased for 3 or greater m.p.h. (except for forested areas where 10 [mu] must be used to obtain penetration). Selection of operation time with respect to meteorological conditions, and mosquito habits is discussed. Residual effects are negligible for the recommended output of 15 gal. per 1000 ft., but a significant protective period may be obtained with short flight mosquitoes. The lethal dosage varies considerably for different insects and the above recommended dosage will not kill "all insects." A local deposition of the order of 0.002 lb. DDT per acre will produce 50% kill on the larvae of Aedes sollicitans and A. taeniorhynchus within 18 hrs. after treatment and depositions of the order of 0.001 lb. DDT per acre will effect 95-100% control of larvae of Anopheles quadrimaculatus within 12 hrs. after treatment.