To understand the molecular events governing smooth muscle cell(SMC) prolifetation in vivo, SMC proliferation and c-myc expression were assessed in aorta in 25 male rats. Balloon-injury to rat aorta evoked platelet adhesion after 24 h and induced increases of SMC proliferation and intimal thickening after 5, 10 and 15 days. c-myc expression increased significantly 24 h, but decreased gradually 5, 10, 15 and 20 days after the injuryThe results indicate that c-myc gene expression corroborates the platelet adhesion and autocrine mode of smooth muscle cells.