Naturally occurring both water and lipid-soluble arseno compounds as well as simple methylated arsenicals which are less toxic than the inorganic species and arsenoribosides are considered to be non-toxic consisting of an interesting group of organometallic compounds. These compounds are of great interest and the structure,function, and also metabolism,partly,has been elucidated. This review focuses primarily on the presence and distribution compounds in vascular plant,marune and freshwater algal species,lichens,fungi,and microorganisms.Some aspects of the metabolism and transformation of arsenic species in mentioned organism will also be discussed.