We report a patients with squamous cell carcinoma of tongue showing transient M-protein (IgG-kappa type) on electrophoresis using a Separax membrane. The M-protein was detected in the alpha 1 to beta regions as a broad band, and it was detected in the slow gamma region as a monoclonal band on electrophoresis using other types of membranes. The unusual electrophoretic pattern of globulin found in this patient was considered to be caused by alternation of globulin by unusual sugar chains.