Background: Interleukin (IL)-17/IL-23 axis performs a prominent role in the pathogenesis of several autoimmune disorders. This study aimed to investigate the concentrations of IL-17 in patients with multiple sclerosis (MS) and its relationship with gender, medication, disease forms and single nucleotide polymorphisms (SNP) in IL-23R gene, including rs11209026 and rs1004819.Methods: The blood specimens were obtained from 135 healthy individuals and 135 MS patients. The patients exhibited relapsing-remitting (RRMS; n = 65), primary progressive (PPMS; n = 19), secondary progressive (SPMS; n = 35) or progressive relapsing (PRMS; n = 14) MS. The DNA was analyzed for SNPs using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and IL-17 concentrations were measured by enzyme-linked immunosorbent assay (ELISA).Results: We have observed elevated serum IL-17 concentrations in MS patients compared with healthy individuals (P < 0.001). The men with MS had higher IL-17 concentrations than women patients (P < 0.050). Untreated patients had significantly higher IL-17 concentrations than healthy individuals and treated patients (P < 0.001 and P < 0.010, respectively). The IL-17 concentrations were significantly decreased in patients treated with interferon-β (IFN-β), methylprednisolone or both drugs as compared with untreated MS patients (P < 0.050, P < 0.020 and P < 0.050, respectively). The IL-17 concentrations were also significantly higher in patients with RRMS and PRMS compared with healthy individuals (P < 0.005 and P < 0.010, respectively). The genetic variations at SNPs rs11209026 and rs1004819 were not significantly different between healthy individuals and patients. The IL-17 concentrations were not influenced by genetic variations at investigated SNPs.Conclusion: These results indicated higher levels of IL-17 in MS patients that may be influenced by disease patterns, medication and gender. No association was observed between investigated SNPs and MS.