The proliferation and migration of vascular smooth muscle cells (VSMCs) play important roles in the formation and progression of intimal thickening in early-phase atherosclerosis and in restenosis after vascular injury. Tumor necrosis factor-${alpha}$ (TNF-${alpha}$) is released from macrophages in atherosclerotic lesions and from neointimal vascular smooth muscle cells after balloon-injury. Obovatol, a major biphenolic component isolated from the Magnolia obovata leaf, is known to have anti-inflammatory and antitumor activities. The goal of this study was to examine the cardioprotective effects of the obovatol derivative OD 78 on the TNF-${alpha}$-induced proliferation and migration of rat aortic smooth muscle cells (RASMCs). The antiproliferative effects of OD 78 on RASMCs were examined by cell counting and [$^3H$]-thymidine incorporation assays. Treatment of cells with $1-4{mu}M$ OD 78 inhibited the proliferation and DNA synthesis of TNF-${alpha}$-stimulated RASMCs in a concentration-dependent manner, without cytotoxicity. Treatment with OD 78 inhibited TNF-${alpha}$-mediated p38 phosphorylation, but did not change the activation of extracellular signal-regulated kinase or c-Jun N-terminal kinase. Furthermore, treatment with OD 78 decreased TNF-${alpha}$-induced levels of cyclin E, cyclin D1, CDK2, proliferating cell nuclear antigen, and phosphorylated retinoblastoma protein, but not the CDK4 expression level. Also, OD 78 inhibits the migration of TNF-${alpha}$-induced RASMC in transwells. OD 78 treatment strongly decreased matrix metalloproteinase-9 (MMP-9) expression in a dose-dependent manner, but the MMP-2 expression was unchanged. These results show that OD 78 may be developed as a potential antiproliferative agent for the treatment of angioplasty restenosis and atherosclerosis.