The environmental fate of fenbuconazole in soil was investigated in a number of laboratory studies using either material labelled in the triazole ring (TR-14C) or uniformly labelled in the unsubstituted phenyl ring (PH-14C). Results of the laboratory aerobic route and rate of degradation studies carried out at 20 or 25°C and either 40% MWHC, 75% or over 100% of Field Capacity were available for 5 soils. One major metabolite (>10% AR) was identified as RH-0118 (1,2,4-triazole) which peaked at 12.4% AR after 363d (study termination). However a further two metabolites (RH-9129 (cis-5-(4-chlorophenyl) dihydro-3-phenyl-3-(1H-1,2,3-triazol-1- yl) methyl-2(3H)-furanone) and RH-6467 (4-(4-chlorophenyl)-2-(methyl-1H-1,2,4- triazole)-4-oxo-2-phenyl butanenitrile)) were detected at >5% in at least two consecutive time points, and may therefore require further consideration. However the Notifier argued that since the study was conducted using a higher temperature (25ºC vs. 20ºC) and longer incubation period (363 days vs. 100 days) than would have been used for a standard European study and that consequently the percentage AR of each degradation product would be expected to be lower at 20ºC and 100 days. In addition, these two minor metabolites have a structure similar to the parent, and contain no additional functional groups that would be expected to significantly increase mobility. Therefore RH-9129 and RH-6467 are expected to have similarly high Koc values to fenbuconazole, and as such are unlikely to present a greater risk of groundwater contamination than the parent compound. The response of the Notifier regarding the metabolites RH-9129 and RH-6467 is considered acceptable by the evaluator and no further consideration of these compounds will be made. Metabolite RH-9130 (trans-5- (4-chlorophenyl) dihydro-3-phenyl-3-(1H-1,2,3-triazol-1-yl) methyl-2(3H)-furanone) was only detected at >5% AR (5.1% AR) in a single sample. The level of 14CO2 recovered from the TR-14C samples was insignificant (=2.3% AR) but reached ca. 12% AR after 90d in the PH-14C samples. Unextracted radioactivity represented ca. 9-45.5% AR after 90-96d in samples from both label positions. The degradation scheme proposed by the Notifier and considered acceptable by the Rapporteur. The proposed aerobic degradation pathway involves initial oxidation on the benzylic methylene to give an unstable hydroxyl compound, which undergoes either further oxidation to the ketone (RH-6467) or intramolecular cyclisation via an intermediate iminolactone (RH-6468) to give the diastereomeric lactones (RH-9129 and RH-9130). These products undergo further degradation resulting in the formation of 1,2,4-triazole (RH-0118) and CO2. In some soils unextracted residues were a significant sink for radioactivity, with peaks of >45% AR present as unextracted residues after 96 d in one soil.