Acetamiprid is a chloropyridinyl neonicotinoid that is widely used in agricultural areas, but its contribution to environmental pollution has resulted in its restriction in many countries. Little information is known about whether bacteria can hydrolyze acetamiprid. A bacterial strain that could hydrolyze acetamiprid was newly isolated using enrichment culture techniques. The morphological, biochemical and phylogenetic analysis characterized the isolate as Stenotrophomonas sp. The maximum growth and acetamiprid-degrading ability of the bacterium were observed at 30 C at pH 7.0, in mineral medium supplemented with 1 gl(-1) acetamiprid. A possibly important metabolite, N-methyl-(6-chloro-3-pyridyl)-methylamine (ACE-3), was identified based on nuclear magnetic resonance and gas chromatography-mass spectrometry analyses. This paper demonstrates for the first time that a pure bacterium is able to hydrolyze acetamiprid by targeting the magic nitro or cyano substituent groups of the compound. The end product ACE-3 is known to be less toxic to mammals and bees. The hydrolytic mechanism is similar to the metabolic conversion of the compound in mammals and insects. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.