In recent with development of immuno-electrophoresis, more acurate analysis of the serum protein became possible. However, there is few reports in the literature which investigated the changes of the immunoglobulin compared with electrophoretically fractioned serum thyroglobulin in the patients with various thyroid diseases. The purpose of this report is to investigate the changes of thyroglobulin in various thyroid diseases by the method of immuno-electrophoresis and to compare the results with serum protein fractionated by the method of agar-gel micro-electrophoresis. Materials and Methods: Sera from 9 patients with diffuse toxic goiter, 2 nodular nontoxic goiter, 2 thyroiditis, 3 hypothyroidism, 1 thyroid cancer, 7 cystic degeneration of the thyroid gland, and 10 normal subject were taken. All cases were confirmed by various laboratory thyroid function tests and thyroid needle biopsy. Immuno-electrophoretic analysis of the serum were performed by Scheidegger's modified micro-immuno-electrophoretic method. The antiserum was obtained from the Travenol Laboratories International, Hyland Products Division and was rabbit anti-human thyroglobulin. Microscope slide agar-gel electrophoresis for serum protein fractionation was performed at 4℃ using veronal buffer, pH 8.6 and ionic strength 0.05, with 54 volts and 2.8mA for 60 minutes. The fractionated slide was stained with 0.1% thiazine red. The results were as follows:1) Increase of immune-globulin macroglobulin (IgM), alphaglobulin, and immune-globulin A (IgA) by 95.8%, 100%, 29.2% respectively was found in the serum from various thyroid diseases. 2) Thyroglobulin fraction was found to be increased in 50%, no change in 41.7%, and no line in 8.3% with all of the various goiter patients. On the other hand, 10 normal control group showed only 2 cases of increase, 5 cases of no change and 3 cases of no line.