AbstractA wide range of crops including top fruit, cereals, brassicas, root vegetables and cotton from field trials in several countries in 1965, 1966, 1967 and 1968 have been analysed for residues of tetrachlorvinphos (Gardona,trans‐homerof dimethyl 1‐(2′,4′,5′‐trichlorophenyl)‐2‐chlorovinyl phosphate) foliar insecticide, its isomer and its potential breakdown products.The residues under field conditions were mainly of tetrachlorvinphos, its isomer and 1‐(2′,4′,5′‐trichlorophenyl)ethan‐1‐ol in free and sugar‐conjugated forms. Tetrachlorvinphos was not unduly persistent on the crops and its initial half‐life varied from 2 days on cabbage, to 7 days on potato foliage and to 12 days on pears (after the last of five applications). From one week after the final application onwards the highest residues of tetrachlorvinphos observed were on olives (1 ppm after 18 days after a single application of 0·1 % active material), maize leaf (2·8 ppm at 9·5 weeks after the last of two applications at 3 kg/ha), and cabbage (1·9 ppm at 12 days after the last of three applications at 0·5 kg/ha). The maximum residues of the alcohol in the free form were 3·2 ppm on maize leaf at 8 weeks from the second application at 1·5 kg/ha and in the conjugated form were 1·0 ppm on cauliflowers at 6 days after t