Dow ET-57 was evaluated as a fumigant against house flies (Musca domestica), yellow-fever mosquitoes (Aedes aegypti), American cockroaches (Periplaneta americana), and confused flour beetles (Tribolium confusum). A procedure for its determination in the air was also developed. The tests were conducted within the fuselage of a C-47 aircraft where the fumigant was applied by blowing air through an impregnated Fiberglas filter. Both the insecticidal effectiveness and the concentration in air were found to increase with the temperature.