Aims: To isolate and characterize atrazine-degrading bacteria in order to identify suitable candidates for potential use in bioremediation of atrazine contamination. Methods and Results: A high efficiency atrazine-degrading bacterium, strain AD1, which was capable of utilizing atrazine as a sole nitrogen source for growth, was isolated from industrial wastewater. 16S rDNA sequencing identified AD1 as an Arthrobacter sp. The atrazine chlorohydrolase gene (atzA) isolated from strain AD1 differed from that found in the Pseudomonas sp. ADP by only one nucleotide. However, it was found located on the bacterial chromosome rather than on plasmids as previously reported for other bacteria. Conclusions: Atrazine chlorohydrolase gene, atzA, either encoded by chromosome or plasmid, is highly conserved. Significance and Impact of the Study: Comparison analysis of atrazine degradation gene structure and arrangement in this and other bacteria provides insight into our understanding of the ecology and evolution of atrazine-degrading bacteria.