The study investigated the effect of reinioside C on the proliferation of vascular smooth muscle cells (VSMCs) induced by angiotensin II (Ang II), which plays a role in arteriosclerosis and restenosis. Treatment with reinioside C inhibited the proliferative effect of Ang II in a concentration-dependent manner. The possible mechanism was found to involve attenuation of Ang II-induced NADPH oxidase mRNA expression, generation of ROS, ERK1/2 phosphorylation, activation of NF-kappaB, and mRNA expression of AP-1 and c-myc in VSMCs. The study suggests that reinioside C inhibits the proliferation of VSMCs induced by Ang II by inhibiting the NADPH oxidase-ROS-ERK1/2-NF-kappaB-AP-1 pathway.