The aerobic route and rate of degradation of phenyl-1-14C methiocarb under dark conditions was investigated in two laboratory studies. The first study used four German soils: a sandy loam, a silt loam soil, a silt soil and a loamy sand. The total recovery of radioactivity ranged from 92.6 to 102.0 % of the amount applied. CO2 was produced at up to a maximum of 50.2% AR at 60 days. Unextracted radioactivity reached a maximum of 57.8% AR at 60 days. The following compounds were identified as major metabolites (i.e.> 10% AR): methiocarb sulphoxide (M01, max 58.8%), methiocarb sulphoxide phenol (M04, max 35.8%), methiocarb sulfone phenol (M05, max 19.8%) and methiocarb methoxy sulfone (M10, max 13.2%). Two minor degradation products were observed during the course of the study. One of these metabolites was identified as methiocarb sulfone (M02) amounting to a maximum value of 2 % of the applied radioactivity (BBA 2.2, day 17). The second minor metabolite observed in a maximum amount of 6.6 % (Laacher Hof AXXa, day 45) and being less than 5 % in all other soils was not identified. The second study used a sandy loam soil from ‘Howe’ (Indiana, USA) and was conducted under aerobic and anaerobic conditions. Under aerobic conditions, total recovery of radioactivity was in the range 100 - –101 %AR. CO2 accounted for 30% AR at 217 days. Unextracted radioactivity reached 43 %AR at 217 days. The major metabolites observed in the study were methiocarb sulphoxide (M01) (max. 30 % at day 29) and methiocarb sulphoxide phenol (M04) (max. 18 % at day 64). The active substance degraded to 3 %AR by 217 DAT. A metabolite identified as methiocarb methoxy sulfone (M10) reached a maximum of 8 %AR at the end of the study (217 days) and had been increasing prior to this point.