Considering the above-discussed role of IL-17A and IL-17F in the pathogenesis of tumors of various origins, we aimed to investigate the effect of functional polymorphisms in the genes encoding these cytokines (IL17A-197A/G SNP, rs2275913 and IL17F 7488 T/C, rs763780), on the risk, progression and prognosis for CRC in patients from the Bulgarian population. This evidence concerns the gene IL17F and colorectal carcinoma.