Arsenic (As), being one of the common elements on earth and also known to be toxic, threatens human health and the environment. In order to survive in As environment, organisms have developed various arsenic resistance (ars) pathways. Prokaryotes that possess arsenic tolerance often contain ars gene clusters/operons, mainly employing the extrusion pathway in conjunction with reductase system. Although over a dozen of ars genes have been identified to date, our investigation reveals that many others still remain un-characterized. Based on a survey of nearly 800 ars clusters, a number of such previously uninvestigated genes are revealed. In addition, there were also over 60 unknown CDS found in the ars clusters. Our work suggests that the variety of proteins involved in the bacterial ars mechanism is much more diverse than currently known.