Geranium sibiricum Linne (GSL) has been used to treat intestinal inflammation in traditional Korean folk medicine. We examined its anti-oxidative and anti-proliferative activity in the Chang liver cells. We determined that GSL glycoprotein isolated from GSL has a molecular weight of 18kDa and consists of a carbohydrate (10.45%) and protein moiety (89.55%). After confirmation of anti-oxidative activity, we investigated the changes in the production of intracellular reactive oxygen radicals (iROS) and nitric oxide in glucose oxidase-stimulated Chang liver cells, because they play a critical role for the cell proliferation as a signal mediator. The results in this study showed that GSL glycoprotein significantly reduced iROS production at 5μg/mL and increased NO production at 20μg/mL in the G/GO system (100mU/mL). Also, our finding indicated that the GSL glycoprotein ((50μg/mL) in the presence of Concanavalin A (Con A, 10μg/mL) resulted in inhibition of proliferating cell nuclear antigen (PCNA, cell proliferation marker). Taken together, GSL glycoprotein inhibits cell proliferation through modulation of intracellular ROS (iROS) and NO in the Chang liver cells. Therefore, we speculate that GSL glycoprotein has an anti-oxidative and anti-proliferative character. Copyright © 2008 Elsevier B.V. All rights reserved.