The postoperative levels of carcinoembryonic antigen (CEA) and the actual half life (T1/2) of CEA were evaluated to ascertain their potency in predicting the recurrence of colorectal cancer after curative surgery in patients who had an abnormally high level of preoperative carcinoembryonic antigen (CEA, > or = 5 ng/ml). Ninety-four patients who underwent curative surgery were enrolled and 24 patients (25.5%) had recurrence during the follow-up period (median: 30 months, range: 2-69 months). T1/2 of CEA for all patients ranged from 1.2 days to 88.1 days, with a median of 4.4 days. T1/2 of CEA (mean +/- standard deviation) was 11.7 +/- 17.9 days in recurrent patients, whereas it was 6.2 +/- 4.9 days in patients without recurrence (p = 0.0224). The patients' age, gender, size of the tumor, location of the tumor, pre-, and postoperative CEA level, pathologic type of the tumor and Dukes stage had no significance in recurrence. The 1-year, 2-year, and 5-year disease-free survival rates were 95.1%, 81.1%, and 73.8% in patients with postoperative CEA levels less than 5 ng/ml (n = 62), respectively, and 71.4%, 64.8%, and 64.8% in patients with postoperative CEA levels higher than or equal to 5 ng/ml (n = 32), respectively (p = 0.04). Patients were divided into Group S (T1/2 of CEA < 4.4 days, n = 43) and Group L (T1/2 of CEA > or = 4.4 days, n = 51). The 1-year, 2-year, and 5-year disease-free survival rates were 95.3%, 85.1%, and 77.7% in Group S, respectively, and 80%, 67.5%, and 64.1% in Group L, respectively (p = 0.0261). In conclusion, the disease-free survival of colorectal cancer patients was prolonged in patients who had a short T1/2 of CEA or a low level of postoperative CEA. In high-risk colorectal cancer patients with an abnormally high level of preoperative CEA, recurrence may be predicted by checking an early postoperative CEA level and/or by a simple calculation of the actual half life of CEA.