Chromium, though in its native state as a metal is inert biologically it has certain biological role in its other forms. Cr(III), specifically in complexed form with certain ligands has been reported to be an essential trace nutrient. For example, Cr(III) in the form of a complex called the glucose tolerance factor(GTF) is believed to enhance the peripheral actions of insulin. On the other hand, Cr(VI) species have been shown to be toxic and mutagenic. However, there are different and sometimes contradictory views are projected in literature by various authors about the role of chromium species in biosystems. The facts are presented in this chapter for the self assessment of the researchers in this aspect of chromium.