To study the involvement of the chemokine receptor CXCR3 and its ligands (CXCL9/Mig, CXCL10/IP-10, CXCL11/ITAC) in optic neuritis (ON).30 patients with ON and 10 non-inflammatory neurological disease controls were included. The patients underwent a phlebotomy, lumbar puncture, and MRI scan. CXCR3 expression was studied on blood and cerebrospinal fluid (CSF) T cells by flow cytometry. CXCL9, CXCL10, and CXCL11 were measured in plasma and CSF by ELISA.CSF concentrations of CXCL10, but not of CXCL9 and CXCL11, were significantly higher in ON patients than in controls. CSF concentrations of CXCL10 correlated with the CSF leucocyte count in ON patients, and CXCR3 expressing cells were significantly enriched in the CSF.These data show that the CSF concentration of the CXCR3 ligand CXCL10 is selectively increased in CSF from ON patients, and CXCR3 positive cells are recruited to the subarachnoid space.