['To establish the relationship between the presence and titer of virus-specific serum- and cerebrospinal fluid (CSF)-antibodies in multiple sclerosis (MS) patients and disease severity measured with different quantitative magnetic resonance imaging (MRI) techniques.', 'We investigated an association between clinical and MRI measures of disease activity and the presence and titer of IgG antibodies against seven common viruses (measles, rubella, herpes simplex virus type 1 and 2, varicella zoster virus, cytomegalovirus (CMV) and Epstein-Barr virus). One hundred and forty (90 female/50 male) patients with definite MS and 131 age and sex-matched controls participated in the study. Antibody positivity and titer were ascertained by the enzyme linked immunosorbent assay (ELISA) technique and clinical assessment was performed by evaluating the expanded disability status scale (EDSS) score and the lifetime relapse rate (LRR). T1- and T2-lesion loads (LL) and the brain parenchymal fraction (BPF) were calculated.', 'Multiple analyses showed that there was an association between antibody positivity against CMV and higher titer and better clinical and MRI outcomes. The cluster analyses indicated that patients positive for antibodies against CMV had significantly older age at onset (uncorr p = 0.001 and corr p = 0.009), lower LRR (uncorr p = 0.003 and corr p = 0.03) and higher BPF (uncorr p = 0.004 and pcorr p = 0.04). CMV-positive patients who had higher antibody titer showed lower T2-LL (uncorr p = 0.003 and corr p = 0.03) and higher BPF (uncorr p = 0.006 and corr p = 0.05).'] Does positivity of cytomegalovirus antibodies predict a better clinical and radiological outcome in multiple sclerosis patients?