Background: Antroquinonol (Antroq) is an active component of Antrodia camphorate. The present study was to validate the preventive effects of Antroq in an atherosclerosis model. Materials and Methods: We examined Antroq inhibitory effect on rat aortic smooth muscle cell proliferation and migration and evaluated its effect on neointima formation and inflammation in mouse carotid artery ligation (CAL). Results: Our data show that Antroq [1] inhibited the proliferation (Antroq [3.0 μg/ml] + PDGF 41.7 ± 7.3%, vehicle + PDGF 134.5 ± 7.3%) (p