Lymphocytic dipeptidylaminopeptidase IV (DP-IV; E.C.3.4.14.5.) is described as a marker enzyme of immunostimulant T-lymphocytes as well as functional characteristic of IL-2-producing cells. Mononuclear cells of periphere blood (MNC) were isolated by density gradient centrifugation followed by enzymcytochemical staining of DP-IV positive cells and measuring of DP-IV enzyme activity using chromogenic substrates. As relative sign of single cell DP-IV activity we calculated average DP-IV activities of DP-IV positive cells. Blood samples from 14 patients with acute virus hepatitis, 30 cases of chronic active liver disease, 61 cases with liver cirrhosis of various kind and 19 patients with fatty liver and toxic hepatitis were investigated. As standard of comparison we used a group of healthy blood donors. By this way significant differences of described DP-IV parameters between some groups of liver disease were evident. Using an aetiologic classification of investigated liver diseases we found highly significant increased single cell activities in hepatitis-B associated cases in comparison to remarkable lower lower values in autoimmune cases. Different hypothesis about changes of lymphocytic dipeptidylaminopeptidase IV as a part of disturbed immunoregulation in chronic liver diseases were discussed.