A carbaryl hydrolase gene (cahA) encoded on the plasmid pRC1 in Arthrobacter sp. RC100 was cloned and sequenced. The entire region of the deduced amino acid sequence was found to be homologous to that of an amidase family. Parts of the consensus sequences of the amidase gene have been identified in CahA from strain RC100. CahA was overexpressed in Escherichia coli JM109, and the enzyme was purified to homogeneity by protamine sulfate treatment, ammonium sulfate precipitation, and hydrophobic and anion-exchange chromatographies. The purified enzyme showed hydrolase activity toward 1-naphthylacetamide and isobutyramide but showed no activity toward I-naphthylacetate. This is the first report of an amidase that is able to hydrolyze N-methyl-carbamate pesticides.