Equilibrium Dialysis is a simple but effective tool for the study of interactions between molecules. Whether it be characterization of a candidate drug in serum binding assays or detailed study of antigen-antibody interactions, equilibrium dialysis proves to be the most accurate method available. Equilibrium dialysis is inexpensive and easy to perform, the only instrumentation required is that used to quantify the compound of interest. Since the results of the assay are obtained under equilibrium conditions, the true nature of the interaction can be studied. Equilibrium dialysis also offers the ability to study low affinity interactions that are undetectable using other methods.