The environmental fate of metaflumizone in soil was investigated in a number of laboratory studies using trifluoromethoxyphenyl, benzonitrile or trifluoromethylphenyl ring labelled material. Results of the laboratory aerobic route and rate of degradation studies carried out at 10, 20 or 27°C are available for metaflumizone for 8 different soils. No major metabolites (>10% AR) were detected under dark aerobic conditions. However the cyclic oxidation metabolite M320I23 (4-(5-hydroxy-3-oxo-4[4- (trifluoromethoxy)phenyl]-6- [3-(trifluoromethyl)phenyl]-2,3,4,5- tetrahydro-1,2,4- triazin-5-yl)-benzonitrile) was detected at >5% AR in at least two consecutive time points (peak occurrence of 8.1% after 187 d in a sandy loam soil) and therefore requires further consideration according to the Guidance Document on the Assessment of Relevance of Metabolites in Groundwater (Sanco/221/2000-rev.10, February, 2003). In addition a number of minor metabolites (<5% AR) were identified; M320I07 (the hydroxy parent); M320I04 (4-(2-oxo-2-[3- (trifluoromethyl)phenyl]ethyl)-benzonitrile); M320I08 (N-[4- (trifluoromethoxy)phenyl]hydrazinecarboxamide); M320I09 (4-(2-hydrazono-2-[3- (trifluromethyl)phenyl]ethyl)benzonitrile) and M320I29 (3-(trifluoromethyl)benzoic acid). Mineralisation to CO2 under aerobic conditions occurred at up to 42.5% AR after 90 d (benzonitrile label at 27°C), up to 2.7% AR after 100 d (trifluoromethoxyphenyl label at 20°C) and up to 11.1% at 91 d (trifluoromethyl label at 20°C). Similarly unextracted residues occurred at up to 25.7% AR after 90 d (benzonitrile label at 27°C), up to 7.2% AR after 100 d (trifluoromethoxyphenyl label at 20°C) and up to 10.7% at 91 d (trifluoromethylphenyl label at 20°C).