One year after treatment of pasture plots with 9 insecticides, there were no statistically significant differences (P=0.05) between numbers of earthworms in treated and untreated plots. Chemical analyses of earthworms obtained 3 weeks after application of the insecticides showed more than 125 ppm of total DDT residues, 22.52 ppm of the sulphone of Dasanit® (O,O-diethylO(p-(methyl sulfinyl) phenyl) phosphorothioate), 9.66 ppm of chlorpyrifos and 26.33 ppm of Bayer 37289 (O, ethylO-(2,4,5-trichloro-phenyl) ethyl phosphonothioate). Other residues were negligible. After one year, residues of only DDT and its metabolites were detected in appreciable amounts.