Experiments were performed to determine the ethylene oxide concentrations and exposure times necessary to kill adult insects of five species: the house fly (Musca domestica L.), American cockroach (Periplaneta americana (L.)), yellow fever mosquito (Aedes aegypti (L.)), confused flour beetle (Tribolium confusum Jacquelin duVal) and Japanese beetle (Popillia japonica Newman). House fly and cockroach eggs were also included in the tests. The insecticide comprised ethylene oxide with propellant 12 (dichlorodifluoromethane) packed in aerosol containers. Drums with air space of 4.7 ft³ were used; details of the experimental apparatus and procedure are given in the short communication. Duplicate tests indicated that the number of hours of exposure at 80°F for 100% pest mortality with doses of 1/4, 1, 2 and 4 lbs/1000 ft³ respectively are: house fly adults 18, 2, 3, 0.5; house fly eggs 2.5, 0.5, 1, 0.5; cockroach adults 18, 2, 2, 0.5; cockroach eggs 18, 2, 2, 1; yellow fever mosquito 18, 2, 1, 0.5; flour beetle greater than48, 6, 2, 1; Japanese beetle 4, 2, 1, 0.5. By comparison, it requires 19 lb of ethylene oxide per 1000 ft³ for a minimum of six hours in enclosed spaces to kill all types of viruses and microorganisms (about 20 times the dose for insects).