Tetracyclines have antiinflammatory properties. To test the in vitro effect of doxycycline in autoimmune neurological disorders of childhood, peripheral blood lymphocytes from multiple sclerosis (n=11), acute disseminated encephalomyelitis (n=12), and control patients (epilepsy and headache, n=12), all aged 5-17, were examined for proliferation, migration, and apoptosis after culture with doxycycline, concanavalin A and myelin basic protein for 48 hours. Doxycycline increased proliferation in the control group, and less in the multiple sclerosis group but not in the acute disseminated encephalomyelitis group (p<0.03). It increased apoptosis in multiple sclerosis patients (p<0.02). According to this preliminary study, doxycycline might have immunomodulatory effects in children, justifying future studies with larger and more homogeneous patient groups.