Mechanistic insight has been gained into the diverse roles played by some chromium(III) ions in biosystems. Experimental evidence to show that chromium may serve to assemble insulin rather than insulin-receptor units has been obtained. A proposal that stabilisation of insulin by Cr(III) may be responsible for the beneficial role of Cr(III) in glucose metabolism has also been made. Although one of the well-known industrial applications of chromium(III) salts has been in the stabilisation of the collagen in skin to produce leather, it has remained difficult to provide a molecular basis to tanning. Results of model studies involving the reactions of collagen with a series of complexes of chromium(III) have been presented and an attempt to provide a molecular basis to the stabilisation of collagen by the metal ion have been made. In view of the growing concern about the ecological consequences as well as the occupational hazards of using chromium, abnormalities induced by a series of chromium complexes on the proliferation of human lymphocytes have been investigated. Evidence for apoptosis by Cr(III) has been obtained. Although chromium plays diverse functional roles in biosystems, a perspective discussion of some common features in the nature of interactions of the metal ion with biomolecules has been attempted.