Recent investigations suggest that proinflammatory cytokines such as IL-6 and IL-8 are involved in the development of colorectal cancer (CRC), whereas statins, primarily used to decrease high levels of blood cholesterol, exhibit pleiotropic effects on carcinogenesis. In the present study we compared the expression of IL-8 and IL-6 in tissue samples of tumor and adjacent normal colon mucosa obtained from patients with advanced colorectal cancer (CRC). The analysis of mRNAs expression for these proinflammatory cytokines determined by RT-PCR showed a higher level of IL-8-mRNA in tumor tissue than in normal mucosa, while IL-6 was similarly expressed in tumor and normal tissue. The mean values of serum levels of both IL-6 and IL-8 were significantly higher in CRC patients than in healthy volunteers. Surgical removal of the tumor resulted in a prompt decrease of serum level of IL-8 already on the third day, whereas IL-6 level was transiently increased to become lower only after 7-10 days. Treatment of CRC with simvastatin (80 mg/day for 14 days) led to a significant decrease of serum IL-6, while the IL-8 level was less affected. The in vitro experiments on colorectal cancer-derived cell lines (HT-29 and Caco-2) demonstrated that application of simvastatin decreased generation of both IL-6 and IL-8. The differences in response of serum levels of IL-6 and IL-8 after tumor removal and treatment with simvastatin are novel observations suggesting distinct pathological roles of the two cytokines in CRC development. We conclude that 1) colorectal carcinogenesis is accompanied by increased synthesis and release of proinflammatory cytokines such as IL-6 and IL-8; 2) simvastatin therapy results in a decrease in serum level of proinflammatory cytokines, especially IL-6 in CRC and 3) simvastatin inhibits release of IL-8 and IL-6 from colorectal cell lines.