Current evidence suggests that multiple sclerosis (MS) results from an autoimmune response mediated by T lymphocytes, which would be activated in the peripheral blood and migrate into the central nervous system. NFkappaB and AP-1 are two main transcription factors involved in T-cell activation. To investigate possible alterations in the activity of these factors in MS individuals, we have assayed NFkappaB and AP-1 DNA binding activity in peripheral blood mononuclear cells (PBMC). Binding activity was analyzed by gel mobility shift assay in MS patients compared with controls. No significant differences were found between the two groups, indicating no evidence of abnormalities associated with MS in NFkappaB or AP-1 binding activities in PBMC, both basally and after PMA+anti-CD3 antibody induction.