The expression of carcinoembryonic antigen (CEA) was analyzed immunohistochemically in 100 colorectal cancer specimens. The tumors were divided into three groups, according to the predominant staining pattern which was either apical, cytoplasmic or stromal. CEA localization was apical in 26 cases, cytoplasmic in 48 and stromal in 26 cases. Overall, well differentiated tumors showed apical CEA, whereas the poorly differentiated tumors showed stromal staining. Significant correlation was noted between the CEA staining patterns and histological grading (P<0.001), nuclear grading (P<0.001), mucin synthesis (P<0.01), blood vessels, lymphatic vessels and peripheral nerve invasion (P<0.01), and lymph node metastasis (P<0.01). CEA staining pattern was not correlated with patients' age, sex or gross appearance of tumors and their site of origin, nor the Dukes' classificcation. It is concluded that the CEA immunoreactivity pattern may provide data that are relevant for the prognosis of the neoplastic disease.