We aimed to assess the significance of three biallelic polymorphisms: IL-17A (rs2275913; G-197A), IL-17F (rs763780; A7488G; His161Arg) and IL-23R (rs11209026, G1142A; Arg381Gln) for RA susceptibility, progression of the disease and response to therapy with TNF-α inhibitors. The gene discussed is IL17A; the disease is rheumatoid arthritis.