In order to demonstrate a prognostic value of preoperative CEA levels, we have tried to define a correlation between CEA and histologic stage of tumor in 124 patients with colorectal carcinoma. CEA concentration has been evaluated by radioimmunologic assay and the histologic stage following Dukes' classification. The results show a 25.0% positivity rate for patients in stage A, 48.2% for stage B, 61.1% for stage C, and 85.7% for stage D. The mean CEA values are 7.8 ng/ml in the first group, 30.3 ng/ml in the second, 58.1 ng/ml in the third, and 134.3 ng/ml in the last group. Furthermore, we have tried to relate the histopathologic grade of the tumor (G) with CEA levels in 54 patients of the 124. We conclude that preoperative CEA has a prognostic value, and it is useful in the staging of colorectal cancer patients. A low concentration indicates an early stage of the tumor, while a high concentration indicates a wide spread of disease; on the other hand, there are not significant correlations with cancer grading.