Immunohistochemical carcinoembryonic antigen (CEA) staining patterns at the invasive tumor margin were correlated with malignant potential in 64 advanced colorectal carcinomas. Twenty-two (34%) carcinomas showed an apical and 42 (66%) a cytoplasmic staining pattern. Carcinomas with a cytoplasmic pattern had a higher incidence of lymph node (71 versus 41%; p < 0.05) and liver (50 versus 23%; p < 0.05) metastasis and higher levels of serum CEA (p < 0.01) than those with an apical staining pattern. Nine of 11 recurrent tumors had a cytoplasmic pattern and 2 had an apical pattern (p < 0.05). Among carcinomas having the same degree of differentiation, those with a cytoplasmic CEA staining pattern were more aggressive. Six (55%) well-differentiated carcinomas with a cytoplasmic pattern metastasized to the liver while none with an apical pattern did (p < 0.05). Moderately differentiated carcinomas with a cytoplasmic pattern had a significantly higher incidence of lymph node metastasis than those with an apical pattern (77 versus 46%; p < 0.05). When colorectal carcinomas are examined at the invasive tumor margin, an evaluation of the CEA staining pattern is useful in recognizing carcinomas having a higher potential to metastasize and recur after curative surgery.