Total RNA of normal human aortic smooth muscle and fatty streaks from thoracic aortawas isolated by acid guanidium thiocyanate-phenolchloroform extraction. The gene expression of PDGFA, B chain and PDGF α- and β-receptor was investigated by Northern bolt analysis. Results In normal aortic smooth muscle or the normal region from the aorta with atherosclerotic lesions, the gene expression of PDGF was very low, while that of PDGF receptor was not detected. In contrast, in the fatty streaks, the expression of PDGF A mRNA and PDGF β-receptor mRNA were augmented significantly. Conclusions It suggests that the increased gene expression of PDGF A chain and PDGF β-receptor pro motes the proliferation of smooth muscle cells thus highly related to the pathogenesis of atherosclerosis.