Plant medications have been used as treatment in various kinds of systemic inflammatory disorder such as Behçet's disease (BD). We investigated the roles of On-Chung-Eum (OCE), a traditional plant medicine, in cytokine regulation of BD. The effects of OCE on cytokine production from phytohaemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMC) of Behçet's patients and control subjects were measured by ELISA. PBMC from patients with active BD produced higher levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) compared to control. OCE significantly inhibited the production of TNF-alpha, IL-1beta and interferon-gamma (INF-gamma), compared to absence of OCE. The inhibitory effects of OCE showed in a dose-dependent manner, and OCE had better effects than immunosuppressive drug, cyclosporin A. OCE is able to effectively inhibit proinflammatory cytokines and immunoregulatory Th1 cytokine. OCE treatment for BD patients may help the improvement of symptoms through cytokine modulation.