['To assess antibody levels against human herpesvirus type 6 (HHV-6), Epstein-Barr virus (EBV), and Chlamydia pneumoniae (CP) in serum from individuals in the early and late phase of MS.', 'A strong association was found between anti-HHV-6 immunoglobulin M antibodies and early MS (clinically isolated syndromes at high risk for MS, and short duration active relapsing-remitting MS) when compared with healthy controls and secondary progressive MS. Moreover, in this group of patients, titers for anti-EBV immunoglobulin G were also elevated. The authors found no association between the levels of serum antibodies against CP and MS, nor did they detect the presence of DNA for these pathogens in the serum of patients with MS. Finally, serum from two patients with other inflammatory neurologic diseases also had elevated immunoglobulin M antibodies to HHV-6, indicating that the presence of this antibody is not specific to MS.'] Is the immune response against herpesvirus more prominent in the early stages of MS?