The serum aldolase activity was determined by the Bruns method in 10 normal subjects and in 19 patients with various hepatic diseases. In normal controls the aldolase activity was found to be 2.8 - 6.5 with an average of 4.9 units. Among 10 cirrhotic patients, six had normal aldolase levels; the levels of the others were within the upper limits of normal; only two patients with cirrhosis had elevated levels.

Increased aldolase activity was found in all of the six patients with viral hepatitis. In one of these patients serum aldolase determinations were repeated at the end of the icteric phase or during convalescence and a marked decrease in aldolase activity was observed. It was high in two patients with obstructive jaundice.

We have concluded that the determination of serum aldolase activity is an important diagnostic tool in acute hepatitis, whereas in chronic hepatic disease the activity is increased only during acute attacks associated with parenchymal damage and therefore its diagnostic value is limited.