The purposes of this study were to analyze the gene expression pattern of antimicrobial peptides, tumor suppressors, growth factors, matrix metalloproteases, and inflammatory cytokines and chemokines in oral irritation fibromas and to identify genes with protective effects against malignant transformation in benign proliferating tumors of the oral mucosa.Biopsies of irritation fibromas (n = 15) and healthy gingiva (n = 15) were obtained during routine surgical procedures. RNA was extracted according to standard protocols, and transcription levels of CCL20, DEFA 1/3, DEFA 4, S100A7, DOC-1, interleukin (IL) 1β, IL-6, IL-8, IL-10, tumor necrosis factor α, Cox-2, matrix metalloproteinase 1 (MMP-1), MMP-2, MMP-3, MMP-8, MMP-9, transforming growth factor β1, transforming growth factor α, and keratinocyte growth factor were analyzed by real-time polymerase chain reaction. In addition, immunostaining was performed to visualize the transcription products of the genes of interest in fibroma tissue as well as in healthy gingiva.The gene expression of S100A7 was 11.3-fold and that of DEFA 1/3 was 14-fold higher in irritation fibromas than in healthy gingiva, whereas the expression of MMP-3 and of inflammation markers IL-1β, IL-6, IL-8, tumor necrosis factor α, and Cox-2 was reduced. Profound down-regulation of DOC-1 gene expression, characteristic for proliferating malignant tumors of the oral cavity, was in irritation fibromas not verifiable.Changes in the expression pattern of S100A7, DEFA 1/3, and MMP-3 seem to be involved in the development of irritation fibromas, whereas chronic inflammation might be of less importance. Overexpression of S100A7, but missing down-regulation of the tumor-suppressor gene DOC-1, might exert protective effects and counteract malignant transformation of benign, proliferating lesions of the oral cavity.