Electrofocused serum and cerebrospinal fluid (CSF) specimens from patients with multiple sclerosis (MS) were analysed for immunoglobulins (Ig) and for antibodies to measles, varicella-zoster and rotaviruses by an imprint immunofixation method. Patterns of intrathecally synthesized antibodies to the 3 viruses differed from patterns of oligoclonal IgG in the CSF. A variable proportion of virus antibody bands (average 19% for measles antibodies, 8% for varicella-zoster antibodies, 31% for rotavirus antibodies) displayed isoelectric points identical to bands of IgG, but absorption with measles, varicella-zoster and rotavirus antigens produced no change in the bands of IgG and no quantifiable decrease of the CSF IgG. The results confirm previous evidence that the intrathecally synthesized viral antibodies so far demonstrated in MS are not carried by the oligoclonal bands of CSF IgG and account for only a minor fraction of the CSF IgG.