Aerobic soil degradation of imazamox was evaluated at 20-25°C using both 14C-pyridine and 14C-imidazolinone (ring) labelled test substance. The degradation of imazamox occurred by oxidation of the methoxy methyl site chain to form the diacid metabolite, CL 312622 (max. 43.6% AR), which was further converted to (form) the hydroxy-acid metabolite CL 354825 (max. 55.2% AR) by decarboxylation of the carboxylic acid site chain. No other metabolites exceeded 5% AR at two consecutive sampling points. The amount of carbon dioxide evolved was very diverse from 1.6% up to 48.1% after 365 days; but often less than10% after 120 days. Unextractable residues accounted for 4.6-21.2% of applied radioactivity after 114 to120 days. The ratio of the two isomers of imazamox and its two major metabolites, CL 312622 and CL 354825 was investigated. According to a study, the ratio of the isomers of parent and both major metabolites remained constant throughout the aerobic and anaerobic soil metabolism and soil photolysis studies. Stability of the isomer ratios for imazamox and its metabolites indicate that the isomers are comparably degradable. The laboratory DT50 values for imazamox and its metabolites, CL 312622 and CL 354825, were calculated according to the current guidance of the FOCUS workgroup on degradation kinetics (FOCUS 2006). Under aerobic soil conditions, the non-normalised DT50 persistence endpoints for imazamox ranged from 10.8 to 397 days. When normalised to 20°C and pF2 moisture, first-order or surrogate first-order DT50 values (where a biphasic fit was superior) for imazamox ranged from 106 to 389 days with a geometric mean (n=6) of 201 days. The kinetic endpoints for both metabolites were derived from the soil degradation studies with imazamox. The non-normalised DT50 values for metabolite CL 312622 were 7.5 to 67.4 days, while the normalised first-order or surrogate first-order DT50 values ranged from 7.4 to 55 days with a geometric mean (n=6) of 24.6 days. The non-normalized DT50 values for metabolite CL 354825 ranged from 110 to 1000 days, while the normalised first order or surrogate first-order DT50 values ranged from 107 to 1000 days with a geometric mean (n=7) of 382 days.