Background/Aims; Monitoring of serum carcinoembryonic antigen (CEA) has been used as a tool to detect recurrence of colorectal cancer postoperatively. This study was planned to evaluate the role of CEA-directed second-look operation (SLO) in treating recurrent colorectal caneer. Methods: Twenty-two patients with recurrent colorectal cancer were included in the CEA-directed SLO. Their primary cancer had been resected curatively and they showed serial and steady increment of CEA above 10 ng/ml. Results: The elevated serum CEA was detected between 5 and 36 months (average, 15 months) after the first surgery. The intervals between elevation of serum CEA and identification of recurrent sites varied from 0 to 8 months (median, 2 months). The site of recurrence was identified in 20 cases (90.9%). Two cases without knowledge of recurrent sites were also confirmed as loco-regional during SLO. The curative resections were performed in 16 cases. The 2-year survival rate was 21% after the curative resection. Although the rate seemed to be not so high, it was significantly higher than that in the patients treated with the conservative surgery. Conclusions: We conclude that thc monitoring of serum CEA is useful to detect the recurrence of colorectal cancer and then to increase survival rate by resection. Even though the site of recurrence cannot be identified after detecting the increase of serum CEA, CEA-directed SLO should be considered in respect to the chance of curative resection. (Kor J Gastroenterol 1998;32:484 - 491)