The degradation of florasulam in soil under aerobic conditions was examined in four biologically viable soils. In case of one soil the test was performed using Florasulam radiolabelled in either phenyl ring or at position C9 in triazolopyrimidine ring (TP labelling). In remaining three soils only TP-radiolabelled test substance was used. Additionally the route of degradation in soil under aerobic conditions was examined in one sterilised soil, in order to determine the degradation mechanisms for florasulam and its soil metabolites. On the basis of the results presented it was stated that the degradation of Florasulam was predominantly biologically mediated (enzymatic hydrolysis of the methoxy- group in the pyrimidine ring), although some abiotic hydrolysis leading to the formation of 5-OH Florasulam also occurred. The degradation of 5-OH Florasulam, on the other hand, can be considered to be as predominantly biologically mediated, with abiotic processes playing a negligible role. This conclusion is valid also for the secondary metabolites. The applicant postulated the degradation of DFP-ASTCA to TSA via DFP-TSA to be the minor route. However, the results of the supplementary study aimed on the examination of the degradation of secondary metabolites in soil may indicate, that in some soils this route may become as important as postulated major mechanism of transformation of DFP-ASTCA – to TSA via ASTCA (both major metabolites).