Abstract. The activities of proteolytic lysosomal enzymes were investigated in serum, leucocytes, liver and muscle of German-Holstein heifers. Altogether there were 119 investigations: 19 9 months, 80 12 months and 20 16 months old female young cattle. Lysosomal enzymes in leucocytes were proven inappropriate for investigation because of very high variation coefficients. The enzymes investigated in serum, liver and muscle only had variation coefficients ranging from 20 to 40% in most cases. The closest connection between activities of individual enzymes was observed in the liver where activities, except for that of lysosomale esterase (EL), were highly correlated with each other. High correlations were calculated between 9 and 16 months old heifers.