We studied 393 endoscopic colonic biopsies from 72 patients, classified in different groups after assessment of their risk factors, using: histologic, histochemical and immunohistochemical techniques (CEA-PAP and PNA-Px). In high risk patients (Groups A and B) the most relevant modifications were dysplasia with hyposecretion and hyperplasia with sialomucin secretion (TR-type change); in Group A 31 adenomas and 19 hyperplastic polyps also were found. A premalignant nature of dysplasia and predysplastic significance of TR change were suggested: 1) by finding the same alterations in mucosa of Group E (colectomized patients for carcinoma at after 1 year); 2) by increasing expression of CEA and PNA-Px ligands; 3) by their absence in Group D (normal controls). Hyperplastic polyps were confirmed not to be premalignant lesions, but since they had peculiar characteristics (increased CEA and PNA-Px positivity, association with adenomas) it does not seem justified to regard them as lesions unrelated to colorectal cancer, especially when associated with other risk factors. CEA and PNA-Px reactivity correlated well with the risk evaluation and with morphohistochemical changes in the mucosa; the reactivity significantly increased from normal mucosa to dysplasia.