Ligusticum chuanxiong (LC) and Angelica sinensis (AS) have been widely used as traditional Chinese medicine to treat some pathological settings such as atherosclerosis and hypertension. The aim of this paper is to determine the effects of the extract of LC and AS (ELCAS) on serum-induced vascular smooth muscle cell (VSMC) proliferation, cell cycle and nitric oxide production. The results show that ELCAS significantly inhibited proliferation and protein synthesis of VSMC in a dose and time dependent manner. The cell population assessed by flow cytometry in the G(0)/G(1) phase increased 74% versus 79.8%, concomitant with a decrease in the S phase, 7.4% versus 4.2%, for control versus ELCAS (300 microg/ml). On the other hand, ELCAS significantly increased nitric oxide production of VSMC. The data suggest that ELCAS markedly inhibited VSMC proliferation by arresting G(1) to S progression, which may be associated with nitric oxide production.