The environmental fate of asulam sodium was investigated in a number of laboratory studies using ring labelled material. Results of the laboratory aerobic route and rate of degradation carried out at 10 or 20°C are available for four different soils. The major metabolite was identified as sulphanilamide which peaked at 14% AR after 14 days at 20�C in clay loam soil. An unidentified metabolite showed levels of up to ca. 20% AR but was found in a supplementary study to be an artefact caused by the scintillant. Bound residues were found associated with all three soil fractions (fulvic, humic and humin) the least radioactivity being associated with the fulvic acids (19 to 32%) and the most associated with the humic acids (22 to 53%) and humin (29 to 67%). The total unextracted residues accounted for 46 to 66% AR. Mineralisation to CO2 ranged from 4 to 6% AR by 59 days and accounted for between 6 to 8% AR after 120 days (study end) in soils incubated at 20�C. The major aerobic degradation path of asulam results in production of sulphanilamide. The major route of dissipation is the formation of unextractable bound residues either of asulam itself but more likely of sulphanilamide. A number of minor metabolites are formed and some of these may be further degraded to carbon dioxide along with a small portion of sulphanilamide. These mechanisms are accelerated by light, without the formation of unique photoproducts, but are slowed by anaerobic conditions.