The promotion of tumor growth is due to a combination of several mechanisms, including angiogenesis and the abundance of cell-derived inflammatory cytokines. The aim of this study was to investigate the serum levels of interleukin 17 (IL-17) and the expression of p53 and Vascular Endothelial Growth Factor (VEGF), in order to determine the relationship between these markers and serum IL-17 levels in patients with colorectal carcinoma. Serum levels of the proinflammatory cytokine IL-17 in patients with colorectal carcinoma (CRC) (n=40) and in a healthy group (n=37) were analysed by ELISA. Surgically resected specimens of 59 colorectal carcinomas were studied by immunohistochemical staining for VEGF and p53. Analyses by ELISA showed significantly higher IL-17 serum levels in patients with colorectal carcinoma than in control subjects (IL-17; mean 128.52+/-47.62 pg/ml vs. mean 101.91+/-22.46 pg/ml; p=0.022). We also found an inverse correlation between p53 expression and the level of IL-17 in the serum of patients with CRC. In fact, the serum concentration of IL-17 was significantly higher in patients who did not express p53 (p=0.023). There was no significant correlation between the expression of p53 and VEGF. However, concomitant expression of VEGF and p53 showed a significant correlation with the histological and nuclear grade of the carcinoma. The data presented in our study indicate that IL-17 might act as a valuable tumor marker in patients with CRC and that combined analysis of p53 and VEGF expression might provide additional information about tumor features.