Aims: We examined the preoperative serum levels of sialyl Lewisa (CA19-9) and carcinoembryonic antigen (CEA) in 262 colorectal cancer patients, in order to clarify whether or not the prognostic value of CA19-9 after curative surgery is superior to that of CEA. Patients and Methods: The patients were divided into two groups: low or high antigen groups (higher or lower than a selected diagnostic-based cut-off value). For evaluation of the prognostic value of CA19-9 and CEA, the disease-free interval was studied. Results: The disease-free interval of patients with a high serum levels of CA19-9 or CEA was significantly shorter than for those patients with a low serum level of the particular antigen (P<0.0001 and P=0.0009, respectively). The disease-free interval of patients with stage I/II tumors who had a high CA19-9 level was significantly shorter than in those patients with stage I/II tumors with low CA19-9 levels (P=0.0020). In contrast, the disease-free interval of patients with stage I/II tumors who had a low or high CEA level did not differ. Cox s regression analysis revealed that a high serum level of CA19-9 or CEA was an independent predictor for short disease-free interval after curative surgery, separate from stage (Hazard ratio=2.65 or 1.68, respectively, versus a low serum level of each respective antigen) . Conclusions: These data suggest that the preoperative serum level of CA19-9 was a stronger prognostic factor after curative surgery than CEA. Furthermore, in contrast to CEA, CA19-9 provides more prognostic information than that obtained by conventional staging methods in patients with stage I/II tumors.