3,4-dichloroaniline- 14C was applied to soil under outdoor conditions, at a rate corresponding to 1.43 kg/ha. Barley was sown immediately after application; in the following year, potatoes were planted. After the first season, a total of 69.8% of the radio-carbon applied was recovered in soil, plants and leaching water, and after the second year the recovery was still 67.1%. Most of the radioactivity was found in the top soil layer (0-10 cm depth). The total radioactivity in barley grains was 0.02 μg/g (equivalent to 3,4-dichloroaniline), the peeled potatoes 0.01 μg/g. Most of the residues in soil and plants was unextractable with organic solvents (50% to 94%); unconverted 3,4-dichloroaniline was about 1% of the residues present after one growing season and less than 1% after the second year's harvest. From purified soil extracts, the following conversion products were identified by chromatographic retention data and by mass spectra of reference compounds: 3,4, 3', 4'-tetrachloroazobenzene (I), 3,4-dichloroformanilide (II), 3,4-dichloroacetanilide (III), and 6-hydroxy-3, 4-dichloroacetanilide (VI). In plants, the conversion products I and III were identified only by Rf-values in various TLC-systems.