Aim To observe the effect of 3,3'-Diindolylmethane(DIM) on C-myc expression in carotid artery injury rabbits.Methods Restenosis model was established by injury of rabbit carotid arteries with balloon catheters.21 rabbits were randomly divided into 3 groups including sham-operated group,model group and DIM group 40mg/(kg·d) once a day from 3 days before operation to 4 weeks after operation,DIM was orally administered to rabbits,while the other two groups with saline at the same volume.All rabbits were killed after 28 days and carotid arteries were removed.We observed artery morphology and measured the thickness of arterial intima and media,examined C-myc with HE staining,automatic image analysis and immunohistochemistry.Results Compared with sham group,the sections of injured carotid artery showed obviously intimal thickening with large numbers of vascular smooth muscle cells(VSMC) proliferating throughout intima and media,the expression of C-myc was markedly increased(P<0.01)after operation.VSMC proliferating was inhibited and gene expression was significantly decreased by DIM.Conclusion DIM can inhibit neointimal proliferation after carotid endothelium injury through down regulation of C-myc expressions.