Long-term observation of serum GOT and GPT activities was performed on patients with viral hepatitis as well as cirrhosis of the liver and without hepatic diseases. 1. Alterations of serum GOT and GPT activities could be classified to 3 types, each of which was further divided into 2 subtypes. 2. A single-peak elevation of the activities was observed in most cases of acute form of epidemic hepatitis. On the other hand, in posttransfusion hepatitis the activity changes were similar to those noticed in recurrent chronic hepatitis: some cases showed a single-peak elevation without discending to the normal level and others exhibited a remarkable fluctuation. Furthermore, in certain cases the fluctuated activities were above normal levels in any measurements. 3. The fluctuation of serum GOT and GPT activities was observed in most cases of chronic hepatitis. Similar results were obtained in precirrhosis and cirrhosis of the liver. 4. Histological findings revealed that inflammation at the portal triads was predominant in cases of chronic hepatitis which showed the fluctuation of serum GOT and GPT activities. This type of activity alterations, therefore, indicates the presence of active foci of hepatitis. 5. Histological changes of the liver were serially examined in those cases of chronic hepatitis and precirrhosis which exhibited the fluctuated activities with consistently elevated values. Degeneration or necrosis of hepatic cells was found to be accompanied with the activity alterations, while the fluctuation was not always in accordance with histological changes related to inflammation, especially with those indicating the chronification of hepatitis. 6. Hence, the fluctuation of serum GOT and GPT activities represents that the disease is progressive in nature, but it does not reflect the histological changes relatad to inflammation, especially those indicating the chronification of hepatitis.