The route of degradation of methomyl in soil under aerobic laboratory conditions has been adequately addressed. Data from radiolabelled studies carried out on four different soils at 20 C and one soil at 10 C resulted in the minor metabolite methomyl oxime (Z-methyl N-hydroxyethanimidothioate, INX1177) being identified at up to 2.5% AR. Methomyl and its extractable breakdown products were readily mineralised to carbon dioxide. At study termination, in 20 C experiments carbon dioxide represented 75%AR at 92 days, 51and 61%AR at 30 days and 51%AR at 21 days. In these experiments and at these times unextracted residues accounted for 14%AR, 32 and 25%AR and 31%AR respectively. It should be noted that in the 92 day experiment, unextracted residues had declined from a peak of 24%AR at days 21-30 indicating further mineralisation of unextracted residues might be expected had the 21 day and 30 day studies been of longer duration.