Infection with Epstein-Barr virus (EBV) is considered one of the possible key environmental factors in the aetiology of multiple sclerosis (MS). Whether EBV plays an underlying role as an activator of MS remains, however, controversial. Sixty-one patients with definite relapsing-remitting multiple sclerosis (RRMS) according to the Poser criteria were followed for 1 year. Blood samples were drawn at baseline, months 3, 6 and 12, and in case of any clinical exacerbation. Twenty-three baseline-paired exacerbation samples in the same set were quantitatively analysed to examine whether exacerbations in MS were associated with a change in anti-diffuse component of the EBV-early antigen (EA-D) IgG ratio. All the 61 patients (100%) were anti-viral capsid antigen (VCA) IgG positive, one (2%) was anti-VCA IgM positive and 60 (98%) were anti-EBV nuclear antigen IgG positive. Mean anti-EA-D IgG at baseline was 0.57 (range 0.12-2.70) and at the time of exacerbations 0.61 (range 0.11-2.70). Wilcoxon signed rank test revealed no differences between the 23 baseline and paired exacerbation samples (P = 0.58). Our findings suggest that reactivation of latent EBV infection does not play a significant role for exacerbations in RRMS.