The aerobic degradation of [14C] dimethipin in soil was investigated in three laboratory studies. Three European and two USA soils were tested. In the first laboratory degradation study a USA sandy loam soil (test conditions: dark, 25°C and 75% 1/3 moisture) was used. Dimethipin was little metabolised. A polar metabolite was found in the water extract of Day 365. However this metabolite represented only 2.3% and consisted of several components. The main residue in soil was the parent compound. After 365 days, 7.4% of the applied radioactivity was trapped as 14CO2. Non-extractable residues reached 36.0 (?? 23.7). The DT50 and DT90 values of dimethipin, assuming first order reaction kinetics, were determined to be 413 and 1371 days. In the second laboratory degradation study two standard German soils (loamy sand soils) and one Swiss field soil (sandy loam) (test conditions: dark, 22±2°C and 40% of the WHCmax) were used. The degradation of dimethipin was mainly based on mineralisation to CO2. After 168 days, 30.2% of the applied radioactivity was trapped as 14CO2. Non-extractable residues reached 18.5- 24.9%. The DT50 and DT90 values of dimethipin, assuming first order reaction kinetics, ranged from 139 to 161 days and from 463 to 535 days respectively. Metabolites were tentatively identified. Two metabolites (H4 and H9) and one unknown polar compound were tentatively identified, but were always below 7%. The DT50 and DT90 values of dimethipin, assuming first order reaction kinetics, ranged from 139 to 161 days and from 463 to 535 days respectively. In the third degradation study a USA sandy loam soil (test conditions: dark, 25°C) was used. Dissipation of dimethipin occurred mainly by adsorption and/or incorporation into the soil organic matter. After 350 days, only 3.1% of the applied radioactivity was trapped as 14CO2. Non-extractable residues reached 34.2%. The DT50 and DT90 values of dimethipin, assuming first order reaction kinetics, were determined to be 673 and 2236 days. Based on existing DT50 values at 22 and 25 °C for dimethipin (DT50= 139- 673 days), the DT50 values at 20°C are estimated to be in the range from 163 to 1004 days (Mean DT50 = 431 days). Based on the DT50 values at 20°C for dimethipin (DT50 = 163 - 1004 days) and a Q10 factor of 2.2, the DT50 values at 10°C are estimated to be 363 to 2234 days (Mean DT50 = 1024 days).