The metabolism of Dipterex in mammals, insects, plants, and microorganisms is discussed. Based on studies with P32- and C14- labelled Dipterex the degradation of the insecticide and the different metabolic pathways are indicated. Whereas the detoxification of Dipterex in mammals and in cotton plant proceeds mainly via hydrolysis of the phosphonate C–P bond, its degradation in microorganisms invokes only O–CH3ester cleavage. In Prodenia larvae, Dipterex is metabolized preferentially (70%) by hydrolysis of O–methyl ester linkages and to a minor extent (30%) by splitting of C–P bond.