Experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the central nervous system (CNS). We previously reported upregulation of gene expression for a number of proinflammatory cytokines, interleukin-1β (IL-1β), IL-2, IL-6, tumor necrosis factor-α (TNF-α), TNF- β, and interferon-γ (IFN-γ), in the CNS of mice with myelin basic protein (MBP)-induced relapsing EAE by using semiquantitative reverse transcriptase- polymerase chain reaction (RT-PCR). However, in these mice there was no significant increase of gene expression for immunoregulatory cytokines (IL- 4, IL-10, transforming growth factor-β [TGF-β]). We report here that gene expression for both proinflammatory and immunoregulatory cytokines increased during the course of disease in the CNS of mice with myelin oligodendrocyte glycoprotein (MOG)-induced nonrelapsing EAE. These results indicate that the gene expression pattern of immunoregulatory cytokines in the CNS may be different between MBP-induced and MOG-induced EAE and that it may influence the type of disease. Accordingly, the course of the disease may be influenced by the interplay between the proinflammatory and immunoregulatory cytokines.