Carcinoembryonic antigen (CEA) in now the most widely used and the most useful marker for many cancers, including those of the colon, lung, pancreas, and breast. Also CEA is widely used for detection, staging, recurrence, and assessing the response to therapy in colorectal cancer. METHODS: From 1992 to 1998 the clinical value of the pre- and postoperative serum levels of CEA who underwent curative surgery at Department of General Surgery, College of Medicine, Dongguk University KyungJu Hospital, in 140 s patient with colorectal cancer with abnormal levels of CEA (>or=5 ng/ml) was investigated. RESULTS: The results are as follows: 1) The positive rate of preoperative CEA level was 47%, so preoperative CEA level measurement was not useful as screening test for colorectal cancer. 2) There was no significant association between abnormal CEA level and the location of tumor. 3) There was significant association between increased levels of preoperative serum CEA and lymph node metastases. 4) The incidence of preoperatively elevated CEA levels in Dukes stages A, B, C, and D was 0%, 27%, 63%, 71%, respectively. There was significant association between increased levels of the preoperative serum CEA and the progressive stages of colorectal cancers. 5) There was no significant association between abnormal CEA level and histologic differentiation of tumor. In addition, there was no significant association between abnormal CEA level and ploidy status of tumor. 6) The recurrence rate was 20% and 77% in patients with preoperative levels of CEA<5 ng/ml and >5 ng/ml, respectively. 7) The recurrence rate was 11% and 64% in patients with postoperative levels of CEA <5 ng/ml and >5 ng/ml, respectively. 8) Considering as normal CEA levels up to 5.0 ng/ml, sensitivity was found to be 77%, specificity, 80%, and predictive value of an elevated CEA concentration, 77%. CONCLUSIONS: In conclusion, it is suggested that measurement of preoperative and serial postoperative CEA is very useful in assessing the prognosis and in detecting recurrences in colorectal cancer.