Colonic carcinogenesis is probably related to a disturbance in cell proliferation of the colonic mucosa. The present study was designed to determine whether patients with adenomatous polyps of the colon, which have a tendency to develop synchronous malignancies of the colon, have any disturbance in mucosal cell proliferation. Using flow cytometry the proliferative index, and the S and G2M phases of normal mucosa and tumoral tissue of patients with colorectal cancer (synchronous, alone, or associated with adenomatous polyps) were studied. No differences were found between the there groups of study at the level of proliferation pattern of normal mucosa. Our findings do not support the development of synchronous or metachronous colon cancer in patients with polyps on the basis of different patterns of cell proliferation.