Under aerobic conditions isoxaflutole was rapidly degraded in soil, with an aerobic half-life between less than 1 and 14 days. The degradation of isoxaflutole predominantly proceeded via ring opening at the isoxazole heterocyclic ring system and rearrangement in the formation of the major (>10% AR) and predominant metabolite diketonitrile RPA 202248. The step can be induced by chemical and biotical processes. Diketonitrile degraded moderately fast further, with a half-life between 10 to 70 days. The biotic degradation of RPA 202248 resulted in the formation of benzoic acid RPA 203328 as a major metabolite. Benzoic acid RPA 203328 itself degraded with a variety of half-lives from less than 5 days to over 1000 days depending on the condition and study. Finally, metabolite RPA 205834 was observed at trace level in aerobic soil degradation tests. The degradation in aerobic soil was accompanied by formation of non-extractable residues (NER). The extent of mineralization was low under the conditions of the laboratory.