Low concentrations of metal ions, particularly those of the first row transition series such as Zn2+, Co2+, Mn2+, Ni2+, Cu2+, and, to a lesser extent, the group IIA ions, Ca2+ and Mg2+, promotes binding of carboxypeptidase G2, alkaline phosphatase and yeast hexokinase to immobilized Procion Red H-8BN, Procion Yellow H-A and Cibacron Blue F3G-A respectively. The binding of ovalbumin to immobilized Cibacron Blue F3G-A and Procion Orange MX-G is selectively enhanced in the presence of AI3+. With ovalbumin and alkaline phosphatase, the effect is almost totally specific for both the metal ion and dye, whereas with carboxypeptidase G2 and hexokinase, metal ions such as Co2+, Ni2+, Mn2+, Cu2+, Ca2+ and Mg2+ also promote binding to varying degrees. Almost all other monovalent and trivalent metal ions appear to be ineffective. Metal ion-bound enzymes can subsequently be eluted with appropriate chelating agents of the amine, aminocarboxylate or substituted pyridine classes.