No major metabolites (exceeding 10% AR at any time point) were detected. Potentially relevant metabolites (exceeding5% AR at 2 consecutive time points) were 4’-OH-pyriproxyfen (max. 0.9-6.3% AR on day 1-14), and PYPAC (max. 1.0-8.6% AR on day 1-14). Besides Pyriproxyfen and the two metabolites mentioned, also DPH-pyriproxyfen ( 0.5% AR), PYPA ( 0.8% AR) and 2-OH-PY ( 0.1% AR) were identified. The maximum level of unidentified fractions accounted for 3.4-9.8% AR in six soils, and in the seventh soil individual levels of unidentified fractions were never >2.0% AR. Mineralisation of Pyriproxyfen in three soils at 25°C was significant: for pyridyl- and phenyl-label, respectively, 28% and 17% AR after 30 days (study end, one soil), 50% and 43% AR after 91 days (one soil) and 24% and 11% AR after 92-94 days (31% and 14% after 180-189 days, one soil). Mineralisation of pyridyl-labelled Pyriproxyfen in four soils at 20°C was also significant: 40-61% AR after 90 days. Non-extractable residues were also formed in significant amounts but never exceeded 70% AR: for pyridyl- and phenyl-label, respectively, at 25°C, maximum 34% and 46% AR after 30 days (study end, one soil), maximum 50% and 52% AR after 28 days (40% and 51% AR after 91 days, one soil) and 39% and 52-58% AR after 92-122 days (maximum 44% and 60% after 149 and 180 days, one soil). Formation of non-extractable residues of pyridyl-labelled Pyriproxyfen in four soils at 20°C was also significant: maximum 33-52% AR after 7-62 days, 30-49% AR after 90 days. Aerobic metabolism of Pyriproxyfen in soil proceeds by several pathways: hydroxylation of the 4- position of the terminal phenyl group to give 4’-OH-pyriproxyfen, cleavage of the ether linkage to give DPH-PYR, and dephenylation to give PYPA. Oxidative breakdown or ether cleavage of primary metabolites gives PYPA, DPH-PYR and 2-OH-PY. The ultimate and major breakdown products are CO2 and non-extractable residues