The behaviour of tebufenpyrad after application to aerobic soil is characterised by extensive degradation. As a result of oxidative metabolism of both the benzene and the pyrazole rings of tebufenpyrad, the metabolites CL 810,719; CL 810,721; and CL 810,723 were formed, all of them charactised by the otherwise intact molecule structure. An additional metabolite CL 810,728 which was detected only in the pyrazole-labelled samples, resulted from cleavage of the amide bond. There were no corresponding metabolites found from the benzene moiety of the molecule after cleavage of the amide bond. This is considered an indication of a rapid rate of metabolism of the cleavage products from the benzene portion of tebufenpyrad. Only two metabolites were detected at levels above 5 % AR. These were CL 810,721 and CL 810,728. All other metabolites remained below 2.7 % AR. The final degradation products were CO2 (27 to 40 % AR after 1 year) via several transient metabolites which could not be identified due to low amounts formed, and bound residues (22 to 40 % AR after 1 year). After the conversion from aerobic to anaerobic incubation conditions, the degradation of tebufenpyrad was almost immediately stopped and the pattern of degradates remained identical to that under aerobic conditions. The amounts of volatiles, metabolites and non-extractable residues did not change significantly compared to the preceding aerobic period. Photolysis studies with tebufenpyrad on soil revealed CL 810,729 to be the major photo-degradation product accounting for up to 12 % AR. CL 810,721 and CL 810,728 were found in maximum amounts of 6.8 % and 5.1 % , respectively.