The purpose of this study was to demonstrate the immunohistochemical localization and distribution of human alpha- and beta-defensins, peptides with antimicrobial activity, in oral mucoepidermoid carcinoma tissue. Tissue samples were embedded in paraffin and alpha- and beta-defensins were immunostained by the streptavidin-biotin coupled peroxidase method. Cancer cells that constituted the ducts, as well as neutrophils, were positively immunostained with the anti-alpha-defensin antibody (HNPs). On the other hand, epidermoid cells and intermediate cells were intensely stained with the anti-beta-defensin-2 (HBD-2) antibody. Mucous-secreting cells were clearly not immunostained with the anti-HBD-2 antibody. The epithelial hyperplasia region adjacent to the tumor tissues was also positively immunostained with the anti-HBD-2 antibody.