The pathogenesis of colon cancer is not well understood. This common type of cancer is generally believed to occur in a multistep process which involves alterations of various tumor suppressor genes and oncogenes during the progression through benign lesions towards carcinoma. TFF3 is a product of the colonic epithelium and has been implicated in colonic mucosal protection and also in the aggressiveness of colon cancer cells. The aim of this study was to analyze the expression of TFF3 during propagation towards cancer development in the human colon. Colonic tissues representing colitis, adenomatous polyposis, tubulovillous adenoma, and mucoid/adeno-carcinomas were processed for immunohistochemistry using an antibody specific for human TFF3. The results were correlated with those of PCNA-labeling, quantified, and compared with those of control tissues obtained from the safe margin of macroscopically normal colonic mucosa of patients with colon cancer. The data showed marked down-regulation of TFF3 expression in adenomatous polyposis, then TFF3 expression returns to about control level during adenoma and remains high during mucoid- and adeno-carcinomas. Colonic tissues with highly invasive cancer cells were characterized by statistically significant down-regulation of TFF3 expression. The changes observed in expression of TFF3 showed an inverse correlation with cell proliferation and suggest that it might play a protective role against colon carcinogenesis.