The route of degradation of diclofop-methyl AE F023408 under aerobic conditions was investigated in two studies (Speer, 1989; Huang and Creech, 2000). Only the study of Huang and Creech can be validated. From the validated study, the predominant route of degradation of diclofop-methyl was rapid hydrolysis to diclofop-acid (maximum of 67.4 and 81.7 % of the AR in the 2 soils tested after 1 day which decreased to 19.1 and 31.3 % after 120 days). Two other minor metabolites were identified, namely diclofop-phenol and hydroxyldiclofop- acid which accounted for a maximum of 5.9 and 3.3 % of the AR. Diclofop-phenol should be considered as a non-transient minor metabolite as it is measured twice at concentrations > 5% (not consecutive) but it is still increasing at the end of incubation. The metabolic pattern under aerobic conditions was identical in the two soils tested. No cleavage of the ether bridge was observed. Therefore potential metabolites with just one ring are transient. The degradation of diclofop-methyl can be complete with a mineralisation of 8.1 to 21.4 % of the AR. Formation of non-extractable residues is the major dissipation process of diclofop-acid, reaching a maximum of 40.8 to 43.6 % of the AR at the end of incubation. The results from the unvalidated study of Speer (1989) indicate that (i) in sterile conditions, the degradation of diclofop-methyl is significantly reduced, (ii) at lower temperatures the metabolism is less pronounced, while (iii) an increase in soil moisture has no significant effect on the dissipation time. No validated study is available to determine the route of degradation in anaerobic conditions. As a consequence, and because diclofop-methyl can be applied in autumn-winter period, an anaerobic study is required. The results from the photodegradation study conducted with diclofop-methyl clearly indicate that this degradation process will not be significant in field conditions. However, as the hydrolysis of diclofop-methyl to diclofop-acid is very rapid and important, a soil phtodegradation study for the diclofop-acid is required.