The changes of serum NEFA concentration after oral glucose administration were examined in patients with acute hepatitis (convalescent), chronic hepatitis, liver cirrhosis and fatty liver, excluding obesity, manifest arteriosclerotic vascular disorders, diabetes and other endocrine disorders. 1) The fasting NEFA value had the tendency to increase in liver diseases, especially in liver cirrhosis. No correlation was found between the NEFA value and the extent of hepatic fatty infiltration. 2) Although no specific pattern of NEFA response to glucose was found in these liver diseases, the decrease in NEFA concentration following the glucose load became less marked in accordance with the increase in the extent of hepatic fatty infiltration.