Abstract When an ionic ligand binds on a protein, the conductivity of the solution changes. An analysis of this change is given. For simple ionic equilibrium models, the concentration of free and bound ligand can be determined. As examples, the binding parameters ( v and K ) of the following systems are determined from the conductimetric titration, and by using Scatchard plots: RNases (A and B) Cu 2+ ; RNases (A and B)/cytidine 3′-monophosphate; and DNase I Mn 2+ . The main advantage of this method being its high sensitivity—very low concentrations and amounts of protein are needed.