Aerobic metabolism studies were performed in 6 different soils: 2 sandy loams, 2 silt loams, a silty clay loam and a clay loam. Clomazone was readily mineralised in the silty and sandy loams, but to a lesser degree inthe clayey loams (in particulare at low temperatures). Soil bound residues accounted for between 1.1 and 30.6% of applied radioactivity, and was found to be dependent on both extraction methods, temperature and the position of the 14C-label, the latter indicating some degree of degradation before incorporation into the soil. The parent compound decreased with between 14.9 and 99.2% in the experiments. No major metabolite exceeding 10% of the active substance was detected under aerobic conditions in the laboratory soil metabolism studies. Up to 9 minor (unidentified) metabolites were noted, contributing in total to a maximum of 7.6% of recovered radioactivity, none individually exceeding amount of 1.6% at each sampling day. Thus, clomazone seems to be the sole major residue in soil under aerobic conditions. However, in an anaerobic soil environment, the formation of one major metabolite, namely N-[(2-chlorophenyl)-methyl]-3-hydroxy-2,2-dimethyl propionamide, occurred at maximum amounts of 37.9% in 2 different soils assayed.