Serum AFP levels were estimated by radioimmunoassay (RIA) at the first and the last but one day of hospitalization of 25 patients with acute viral hepatitis of type A. The observed group consisted of 11 women and 9 men. A significant increase in the serum AFP levels was found in the group of patients on the first day of hospitalization. Besides, a rise in the aminotransferases (ALT and AST) activity and in the serum total bilirubin level were observed. On the last but one day of hospitalization the mean value of serum AFP level and the activity of the investigated enzymes were diminished. Mean value of serum AFP level the and activity of aminotransferases were higher in patients than those in the control group. Only serum total bilirubin level was similar to the mean value of control group.