We investigated the levels of CEA, CA 242,CA 19-9 and the total antioxidant status in 45 patients with colorectal cancer. Blood samples were obtained from 24 patients in the early postoperative phase, 16 patients in the late postoperative phase and 5 patients with recurrent disease. Statistical significances were calculated in each group by the Mann-Whitney U test. No meaningful difference was observed between the control and early or late postoperative groups. However, serum CEA levels were significantly different between the control and recurrent groups (p < 0.001). A meaningful difference was also observed between the recurrent and early (p < 0.001) and late postoperative (p = 0.015) groups, respectively. Our study shows that CEA is the only tumor marker that can be used in monitoring colorectal cancer patients.