Aerobic metabolism of novaluron in soil proceeds via microbial pathways by cleavage of the urea linkage at various positions and is similar to that observed during hydrolysis studies in water, although degradation under environmentally relevant conditions is mainly microbially mediated. During laboratory studies of aerobic incubation in four soils (40% MWHC, pH 6.2-8.8, %OC 0.8-3.7%, 20􀁱C), novaluron degraded with DT50s of 5-13 days and DT90s of >120 d (2nd order and bi-exponential kinetics) and in one soil at 10􀁱C with a DT50 and DT90 of 20 and >120 d , respectively. Up to 14 degradates were characterised. The only major metabolite (>10% AR) was 275-352-I (maximum 18.1-26.6%, day 7). Two minor metabolites were identified as 275-309-I (chlorophenyl label) and 275-158-I (difluorophenyl label). Mineralisation was significant with the difluorophenyl label but not with the chlorophenyl label, as shown by CO2 levels of 22.5% AR and 2.3% , respectively, on day 90. Non-extractable residues accounted for up to 46.7 % AR after 120 days. Of the unextracted residues, the majority was associated with insoluble humins and therefore likely to be unavailable. The degradation rate of novaluron showed a tendency to decrease with decreasing temperature. Data on the degradation of 275-352-I obtained during aerobic degradation studies on the parent compound give variable (best-fit) rate order DT50s of 13- 32 days. Acceptable first order kinetics fitted to these data for the purpose of modelling gave DT50s of 41-46.4 days.