The aim of this study was to assess the utility of determining serum levels of the CEA, CA 19.9 and CA 195 tumor markers in 906 patients with colorectal carcinoma for a 5-year follow-up period. In addition to calculating sensitivity and specificity for the common normal limits, the results were analyzed with RO curves. Sensitivity values for 90% and 95% specificity were also obtained. The results of the areas under the curve (CEA: 0.887; CA 19.9: 0.802; CA 195: 0.971) and sensitivities and specificities at different normality limits showed better behavior for CEA with respect to CA 19.9 and CA 195, the last two presenting similar results. CEA continues to be the best tumor marker to monitor patients with colorectal carcinoma.