The first case of macromolecular GOT was reported by lida et al. in 1973, and since then only 11 cases have been reported. In the present paper, we report two cases of abnormally elevated serum GOT, which was difficult to explain by organic disorders. Using various biochemical and immunological methods, the GOT was concluded to be macromolecular GOT. Sephadex G-100 column chromatography was carried out to estimate the molecular size. After dividing the GOT into isoenzymes by Cellogel membrane electrophoresis, the GOTs were dyed using the GLDH method developed by Lippe. The immunofixation method was used to examine what kind of immunogloblin combined with GOT. Case 1 was a 69-year-old woman with angina pectoris and hypertension. Her serum GOT level was 279 IU/l. Her serum GOT was found to be combined with IgG-x. Case 2 was an 8-year-old boy who suffered from bronchial asthma. His serum GOT levels were highly elevated (192IU/L). The GOT was combined with IgG-λ. In both cases, we estimated the GOT molecular weight to be 14,0000 Daltons.