Experimental autoimmune encephalomyelitis (EAE) is an animal model for multiple sclerosis in humans. EAE can be passively transferred into naive syngeneic animals by administration of MOG-specific T cell clones. Lymphocytes isolated from green fluorescent protein (GFP)—transgenic (Tg) mice can light up by emitting green fluorescence, thus making it feasible to use such animals in a passive transfer model for EAE. When MOG-sensitized splenic lymphocytes from GFP-Tg mice were adoptively transferred to irradiated, syngeneic C57BL/6 and RAG-1^−/−mice, typical symptoms of EAE developed. Analysis of the reconstituted mice with EAE revealed prominent infiltration of fluorescing (GFP⁺), CD4⁺T cells into the central nervous system (CNS). Real-time confocal imaging revealed these cells in the spinal cords and brains of recipient mice. This infiltration was also confirmed by anti-GFP monoclonal antibodies. Furthermore, quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) evaluation indicated that the infiltrating GFP⁺, CD4⁺T cells exclusively produced T helper type 1 (Th1) cytokines, especially interferon-γ (IFN-γ). These results clearly show that MOG-specific CD4⁺T cells preferentially invade into the CNS and mediate the development of EAE by producing Th1-biased cytokines.