AIM: The aim of this study was to compare the preoperative and postoperative (48th hour) total serum sialic acid levels of the patients with colon cancer and to investigate if the total serum sialic acid levels can be used as a tumor marker in colon cancer. METHODS: Preoperative and postoperative (48th hour) total serum sialic acid levels of 100 patients that were diagnosed with colon cancer and 70 healthy individuals were examined. All total serum sialic acid levels were determined by the methods of Warren. RESULTS: Total sialic acid levels of both patient groups were significantly higher when compared to the control group (p<0.0001). Also, highly significant difference was found between preoperative and postoperative total serum sialic acid levels (p<0.001). CONCLUSION: Evaluation of total serum sialic acid levels may play a critical role in colon cancers. Total serum sialic acid levels may serve as a non-invasive tool for early diagnosis of colon cancer.