The interleukin (IL) -23/IL-17 cytokine axis has been suggested to play an important role in the development of several autoimmune diseases including multiple sclerosis. Here, we compared the prevalence of C2370A single nucleotide polymorphism (SNP) in the 3' untranslated region (3'UTR) of the IL-23 receptor (IL23R) between 223 patients with relapsing-remitting multiple sclerosis (RRMS) and 200 healthy controls. The A2370A genotype was significantly over-represented among patients with RRMS (10.8%) and RRMS exhibiting oligoclonal bands in the cerebrospinal fluid (12.9%) when compared to healthy subjects (5.50%). Multiple regression analysis revealed that presence of AA genotype provides a two-fold risk for the development of multiple sclerosis (OR=2.072, 95% CI: 0.988-4.347, p<0.05). These data indicate that IL23R represents a novel shared susceptibility gene as its association with inflammatory bowel disease (IBD) has recently been verified.