Abstract：Objective To explore the clinical significance of the changes of serum CEA, CA72-4, HCY and Cys C levels both before and after operation in patients with colon cancer. Methods Serum levels of CEA, CA72-4, HCY and Cys C in 31 patients with colon cancer before and after operation as well as in 35 health controls were determined by RIA, immunochemistry and latex–enhanced immunolrubidimetry. Results The serum levels of CEA, CA72-4, HCY and Cys C in the patients before operation were significantly higher than those of the controls (P<0.01). The serum levels of CEA, CA72-4, HCY and Cys C in 28 of postoperative cases without recurrence at 6 months dropped markedly and approached to normal level as in controls. However, the serum levels in 7 patients with recurrence increased and approached to levels as before the surgery (P<0.01). Conclusion The serum levels of CEA, CA72-4, HCY and Cys C might be used as indicators for diagnosis and predicting therapeutic efficacy after operation in patients with colon cancer.