Objective: IL-10 is a cytokine that plays a complex role in the control of immune responses. A case-control study was conducted to investigate the expression pattern of IL-10 in both serum and the whole unstimulated saliva from ethnic Chinese patients with oral lichen planus. Method and Materials: Seventy-nine Chinese patients with oral lichen planus were recruited for this study, and 41 healthy volunteers served as a control group. The levels of IL-10 and IFN-g in the serum and saliva were detected using enzyme-linked immunosorbent assay (ELISA). The IFN-g/IL-10 ratio was calculated by direct counting. Results: The results demonstrated an expression profile of high IL-10 level and low IFN-g level and IFN-g/IL-10 ratio in both serum and saliva from oral lichen planus patients, compared to the controls. Saliva levels of IL-10 and IFN-g were positively correlated to their serum partners. No significant difference was found among subtypes of oral lichen planus. Conclusion: Elevation of IL-10 level might be involved in the pathogenesis of oral lichen planus, and saliva might be a substitute for serum to reflect the disease-related cytokine production in oral lichen planus patients. Keywords: cytokine, oral lichen planus, saliva, serum