Variants of the gene coding for interleukin 23 receptor (IL23R) have been confirmed to be associated with inflammatory bowel disease (IBD). Based on similarities in the autoimmune features of IBD and multiple sclerosis (MS), we selected this gene for analysis as a candidate gene in MS. We tested 32 single nucleotide polymorphisms tagging all parts of the gene including 10 markers previously studied in IBD for association with MS. The study population consisted of 1114 MS patients and 1235 controls of Scandinavian origin. None of the tests showed more than very modest differences between patients and controls. Haplotypes were constructed and were also similarly distributed in patients and controls. We conclude that it is unlikely that the IL23R gene confers any significant risk for MS.