A general discussion of the problem of aircraft disinsection is presented. The weaknesses of the present aerosol method, the limitations imposed by airline operators, government officials, passengers, and others, and the potential value of insecticidal vapours as a means of aircraft disinsection are discussed. An apparatus is described for screening insecticides for their vapour toxicity to houseflies and mosquitos. This apparatus led to the discovery of DDVP (O,O-dimethyl-2,2-dichlorovinyl phosphate) and its remarkable vapour toxicity to insects, and to the subsequent studies of its potential use in the vapour state for aircraft disinsection.