Methods are described for detecting insecticides in dead bees. Bees received by the Chief Bee Advisory Officer of the Ministry of Agriculture, Fisheries & Food have been analysed by these methods and it is evident that each year some are killed by insecticides. Most such happenings are in Eastern England and are caused by spraying, especially from the air, with organo-phosphates to control aphids on pea and bean crops. The use of poison baits to kill wasps is another cause. Such happenings could mostly be prevented by taking a few elementary precautions.