Zymosan-induced stimulation of mononuclear phagocyte system was used as a model for study of inflammation in vivo. Zymosan administration to mice was followed by increase of macrophage enzyme markers beta-N-acetylglucosaminidase and beta-N-acetylgalactosaminidase activity in liver and serum. Serum acid glucosidases secretion occurred both after macrophage stimulation by zymosan and macrophage depression induced by GdCl3. Liver granulomatous inflammation resulted increased activity of liver cathepsin B and cathepsin L. There was no changes of cysteine proteinases studied in the case of macrophage depression by GdCl3. The role of lysosomal enzymes secretion in macrophage stimulation and inflammation was discussed.