The active substance S-2200 (mandestrobin) is a racemic mixture (1:1) of the two isomers S-2167 (S-2200 R-isomer) and S-2354 (S-2200 S-isomer). In order to determine the route of degradation of the active substance mandestrobin (S-2200) in soil separate studies with the two isomers were conducted. No isomerisation occurred during any of the studies. The route of degradation under aerobic conditions was assessed for both isomers (S-2167 and S-2354) separately on six EU soils (pH 5.5-7.7, OC 1.3-3.8 %). Under standard aerobic conditions (20 °C), S-2167 (labelled in the benzyl- or phenoxy-ring) degraded mainly to CO2, bound residues and up to five metabolites. Levels of CO2 after 120 days incubation were in the range of 4.2 – 34.4 % of AR. Levels of bound residues increased steadily during the study period to reach at the end of the study values between 6.7 % and 33.2 % of AR. The metabolite 5-COOH-S-2200 was detected as a major metabolite reaching up to a mean maximum of 19.7% of applied radioactivity after 59 d. The metabolite 2-COOH-S-2200 was present at ≥ 5% and ≤ 10 % with a mean maximum of 8.7 % of applied radioactivity after 60 d. The metabolite DX-CA-S-2200 was detected at a maximum of 3.3 % 120 DAT and the metabolites MCBX and De-Xy-S-2200 did not exceed 1% in any soil at any timepoint. All other metabolites individually accounted for less than 3%. The route of degradation of S-2354 is very similar to that of S-2167: S-2354 (labelled in the benzyl-ring) degraded mainly to CO2, bound residues and up to five metabolites, too. Levels of CO2 after 120 days incubation were 4.4 –27.1 % of AR, levels of bound residues were between 6.4 % and 29.7 % of AR at the completion of the 120 days incubation. The major metabolite 5-COOH-S-2200 reached up to 16.1 % of applied radioactivity after 60 d. All other metabolites, including 2-COOH-S-2200 (max. 4.8 % AR, 120 DAT), DX-CA-S-2200/De-Xy-S-2200 (max. 4.1 % AR, 120 DAT), MCBX (<1 % AR) and unknown metabolites, individually accounted for less than 5 % AR. The route of degradation was qualitatively and quantitatively the same for both isomers. Based on the combined results for the racemate, the metabolite 5-COOH-S-2200 reached a maximum of 18.0 % and the metabolite 2-COOH-S-2200 reached a maximum of 6.7 %.