The effects of tunicamycin(TM) and 2-deoxy-D-glucose(2-D-G) treatment on the specific activities and isozyme patterns of the cellular and secretory peroxidases of tobacco callus were investigated. The specific activities of the cellular peroxidases were increased by TM and 2-D-G treatment during entire culture periods, whereas the specific activities of the secretory peroxidases were decreased by TM and 2-D-G treatment. Comparisons of the isoperoxidase patterns of TM treated groups and 2-D-G treated groups with those of control groups showed that both TM and 2-D-G cause the significant elevation of the activities of cathodic isoperoxidases, especially isoperoxidase C₄ which is a glycoprotein. But the decrease of the specific activities of the secretory peroxidases by TM and 2-D-G was mainly due to the lowered level of anodic isoperoxidase A₃ which is also a glycoprotein. Immunoprecipitation with anti-A₃antibody and anti-C₄ antibody were carried out to examine the changes in the synthesis and secretion of these isozymes due to the treatment of the callus with the glycosylation inhibitors. These results suggested that the increase of cellular C₄ activity was due to the increased amount of C₄ proteins and the decrease of the activity of secretory isoperoxidase A₃ was caused by the decrease of A₃ proteins in the medium in the presence of the glycosylation inhibitors.