BACKGROUND /AIMS: The aim of this study was to calculate the prevalence of elevated carcinoembryonic antigen (CEA) among colorectal cancer (CRC) patients and to evaluate the prognostic value of preoperative serum CEA levels in them. METHODS Between 1995 and 2005, 8,861 consecutive patients were enrolled from a prospective database. CEA =5ng/mL was defined as elevated CEA. RESULTS In the multivariate analysis, elevated preoperative CEA correlated with higher ages, circumferential tumors, colon tumors, large tumors, liver metastasis and high-stage (AJCC) tumors. After a 44-month median follow-up, elevated CEA was found to be an independent prognostic factor (odds ratio = 1.61) for overall survival in all 4 stages of the disease. The survival among patients with stage I tumors and elevated CEA (5-year survival rate = 74.7%) was not greater than that among patients with stage II tumors and no CEA elevation (5-year survival rate = 80.8%). CONCLUSIONS Elevated preoperative CEA correlated with a higher age, circumferential tumors, colon tumors, large tumors, liver metastasis, and high-stage (AJCC) tumors. Elevated preoperative CEA indicates a potential poor prognosis even in early stage tumors. This poorer prognosis in the patients with stage I tumors and elevated preoperative CEA was not cancer specific.