Abnormal low molecular weight immunoglobulin heavy chain can be detected in serum samples from patients with heavy chain disease. In this paper, we report the characterization of a gamma heavy chain in a patient suffering from a lymphoplasmocytic disorder, using immunofixation analysis and two-dimensional polyacrylamide gel electrophoresis. We demonstrate that the combination of serum protein agarose electrophoresis and two-dimensional electrophoresis (three-dimensional electrophoresis) can be used to further characterize abnormal protein bands detected by immunofixation.