AIM: The significance of preoperative serum IL-6, TNFα and CRP levels in the progression of colorectal cancer (CRC) has not been fully elucidated. Our intention was to investigate their role and identify their prognostic significance. METHODS: The IL-6, TNFa and CRP levels were measured in 74 CRC patients and the relationships between their elevations and both the clinicopathological factors and prognosis of patients were investigated. Serum concentrations of human IL-6 and TNFα were determined by enzyme-linked immunosorbent assay (ELISA). CRP was measured by an immunoturbinometric method. RESULTS: Median IL-6, TNFα and CRP levels were significantly higher in CRC patients than in normal controls. High levels of serum IL-6, TNFα and CRP were correlated with larger tumor size. Furthermore, high IL-6 and high CRP levels were associated with reduced overall survival. CONCLUSION: Serum IL-6, TNFα and CRP levels definitely increase in CRC patients. Pre-operative serum elevation of IL-6 and CRP was thus found to be predictor of the prognosis of CRC patients. The clinical value of TNFα in CRC needs to be further investigated.