Environmental factors, in particular infections, have been linked with the risk of developing multiple sclerosis (MS). The association of Epstein-Barr virus infection with childhood onset of MS has been recently recognized. As other infections characteristically experienced during childhood have not yet been studied in larger cohorts of paediatric MS, we conducted a study on 152 German children with MS (age at onset <16 years) and matched controls in the hope of gaining evidence for their possible aetiological role in MS. Patterns of antibody responses were determined to a range of infections which, in prior studies principally on adult patients, had revealed possible associations with MS. In this study on children the serology of several infections showed associations with MS. In the exceptional case of Chlamydia pneumoniae there was a significantly higher prevalence of IgM antibody but, more typically, as in the case of influenza A, measles, parainfluenza 2, varicella/zoster viruses and particularly to the herpes simplex virus type 2 (HSV-2) lysate antigen, there were significantly higher concentrations of IgG antibody. Additional investigations, however, make it highly unlikely that a relevant number of children have experienced infections with HSV-2. In general this study supports and emphasizes a complex infectious and immunologic background of MS.