Penoxsulam is rapidly converted to the 5-hydroxy (5-OH) metabolite by microbiological degradation. Further degradation of the 5-OH metabolite occurs to give BSTCA. BSTCA is further degraded to at least three minor metabolites including BST, SFA and BSA. The 5-OH and BSTCA metabolites are the only two metabolites that exceed 10% of applied. Mineralization to carbon dioxide was less than 2% and non-extractable residues reached a maximum of 10-16% after 120 days. Under aerobic conditions at 20 °C, the first-order DT50 was 22 to 58 days (average 32 days). The degradation rate is influenced by temperature, with a DT50 of 132 days at 6 °C and 15 days at 30 °C.