We previously observed Th1-dominated response in the central nervous system (CNS) of mice during the course of experimental allergic encephalomyelitis (EAE) with a semiquantitative reverse transcriptase-polymerase chain reaction (RT/PCR) analysis. We report here that mRNA levels for both inflammatory cytokines including interleukin (IL)-1beta, IL-2, IL-6, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha and TNF-beta and immunoregulatory cytokines including IL-4, IL-10 and transforming growth factor (TGF)-beta were up-regulated in the preclinical and/or acute phase but down-regulated in the recovery phase of EAE in lymph node (LN) of mice. Similar profiles for cytokine mRNA levels were also observed in spleen and peripheral blood mononuclear cells (PBMC). The present study also showed that a significant down-regulation of the mRNA level for IL-6 in the acute phase as compared with the preclinical phase, and a significant reduction of the mRNA level for TGF-beta in the preclinical and acute phase as compared with the corresponding mRNA levels in the control mice treated with complete Freund's adjuvant alone were characteristic in peripheral immune organs of mice with EAE. These results indicate that no particular bias in cytokine production occurred in peripheral immune organs of mice with actively induced relapsing EAE, and that the relative reduction in production of TGF-beta or IL-6 in peripheral circulation might participate in the induction or remission of EAE, respectively. Our results using the animal model of multiple sclerosis (MS) suggested that the mRNA levels for IL-6 and TGF-beta in PBMC from patients with MS may be a good indicator to assess the disease activity or to predict relapse.