Abstract: Proliferation of vascular smooth muscle cells(VSMCs) represents an important event in vascular lesion formation. In the present study, we investigated whether heparinoid abstracted from porcine duodenum inhibits the proliferation of rabbit aortic VSMCs in vitro, using the method of colorimetric MTT (tetrazolium). Our results showed that heparinoid at 1.6～0.05 mg·ml^-1 significantly inhibits VSMCs proliferation induced by fetal calf serum(FCS,10%), basic fibroblast growth factor(bFGF, 50 ng·ml^-1) or interleukin-1(IL-1, 50 u·ml^-1).In inducing with bFGF, the inhibitive effect of heparinoid was more potent than that of heparin, while in inducing with FCS or IL-1,the inhibitive effect of heparin was more potent than that of heparinoid. Preincubation with heparinoid at 0.2～0.05 mg·ml^-1, the vascular smooth muscle cell proliferation induced by FCS was also inbibited. Our results imply that heparinoid may be useful to protect the atherosclerosis and angioplasty restenosis.