Osteopontin (OPN), also known as early T-cell activating gene (Eta-1), has been recently shown to be a critical factor in the progression of experimental autoimmune encephalomyelitis, and perhaps multiple sclerosis (MS). Here we investigated whether the 327T/C, 795C/T, 1128A/G or 1284A/C single-nucleotide polymorphisms in the OPN gene were correlated with susceptibility or any of the several clinical end points in a cohort of 821 MS patients. Overall, we observed no evidence of genetic association between the OPN polymorphisms and MS. Although not reaching statistical significance, a modest trend for association with disease course was detected in patients carrying at least one wild-type 1284A allele, suggesting an effect on disease course. Patients with this genotype were less likely to have a mild disease course and were at increased risk for a secondary-progressive clinical type.