Summary:Chlortoluron hadàhalf‐tire in soil of 4–6 weeks. The only metabolite identified was monomethyl chlortoluron, half‐life 8 weeks. 3‐Chloro‐4‐methylphenylurea hadàsimilar half‐life but was not detected in soils treated with chlortoluron or monomethyl chlortoluron suggesting that 3‐chloro‐4‐methylaniline was formed directly from monomethyl chlortoluron. This aniline hadàhalf‐life of 1–2 days in soil, initial concentrations above 5 ppm yielding dimers and trimers predominantly C — N linked. Neither the aniline nor polymeric products were detected in chlortoluron treated soils, presumably because slow formation of the aniline was followed by rapid degradation