DDVP (O,O-dimethyl-2,2-dichlorovinyl phosphate) is an organic phosphorus insecticide proposed for use in the disinsection of aircraft at vapour concentrations within the range of 0.15-0.25 mug per litre of air for 30 minutes. Safety tests have shown that men can withstand brief exposure to concentrations as high as 6.9 mug per litre and daily 8-hour exposure to concentrations as high as 0.5 mug per litre without clinical effect and with little or no depression of blood cholinesterase. It would appear, therefore, that DDVP could be safely used at the concentrations and exposure periods required for the disinsection of aircraft, though further studies will have to be carried out before this procedure can be definitely recommended.