A standard aerobic degradation study under non-sterile laboratory conditions led to quinmerac degrading fully after 120 days. Aerobic degradation led to the formation of two metabolites; BH 518-2 (max 29% AR) and BH 518-5 (max 27% AR). The metabolite BH 518-4 was detected in an acceptable but non-standard rate of degradation study at a maximum level of 2.5 %AR, and it appears that this is a transient metabolite that is rapidly transformed to BH 518-2. It was also noted from this non-standard study that higher levels of metabolite formation were seen under different conditions, up to 42.2% AR as BH 518-2 at 5􀃛C and 60% of field capacity, and 34.7% AR as BH 518-5 at 10􀃛C and 60% of field capacity. CO2 was found at a maximum of 40% over the study period. Unextracted residues of quinmerac at 91 days ranged between 43-52%, these unextracted residues were then further characterised for one of the soil types studied; a maximum of 15% AR was recovered in the fulvic acid fraction (comprising of a maximum of 5% quinmerac and 2.5% BH 518-5), 12% AR in the humic acid fraction and 18% AR remained as residue in the humin fraction. An aerobic study was also conducted at 10°C; under colder conditions quinmerac was degraded more slowly resulting in a DT50 value of 106 days. The Notifier proposes that the metabolisation of quinmerac in soil can start at two positions within the molecule; either the 3-methyl group is stepwise oxidized forming the respective alcohol (BH 518-4) and finally the carboxylic acid (BH 518-2), or the quinoline structure is oxidized in 2-position forming the hydroxylated parent (BH 518- 5). Both pathways finally lead to the formation of large amounts of CO2 and nonextractable residues. The formation of CO2 indicates that the quinoline ring structure is opened and further degraded. The formation of non-extractable residues indicates that either the parent structure itself or possible degradation products were used as structural elements for the formation of humic substances.