Abstract: Objective The present study was designed to elucidate the effect of baicalin on the proliferation of vascular smooth muscle cells (VSMCs) and the neointimal hyperplasia after balloon injury and the related mechanism. METHODS Cell culture, MTT assay, Western blotting and immunohistochemical staining were adopted to evaluate the inhibitory effects of baicalin on VSMC proliferation. RESULTS Baicalin inhibited cell proliferation induced by PDGF in a dose-dependent (5、10、20、40 μmol/L) manner, reduced proliferating cell nuclear antigen (PCNA) expression and blocked PDGFR-MEK-ERK1/2 signaling pathway activated by PDGF in VSMCs. In vivo, baicalin significantly inhibited neointimal hyperplasia induced by balloon injury. The ratio of intima-to-media area (I/M) in baicalin group was significantly less than that in balloon injury group (P<0.01). The expression of PCNA, ICAM-1 and VCAM-1 were significantly reduced in baicalin group, compared with the balloon injury group. CONCLUSIONS Baicalin inhibits neointimal hyperplasia via inhibiting VSMC proliferation and adhesion molecule expression induced by balloon injury.