Aim This study is to investigate wether insulin may stimulate the proliferation of vascular smooth muscle cells and the expression of proto-oncogene c-fos and c-myc in the DMEM which had different concentration insulin.Methods The human umbilical arterial smooth muscle cells were incubates with the DMEM which had different concentration insulin,(0,10,100,1000,10000μg/l).We ued trypan blue staining to count the cells and cultured the thind SMC with H-thymidine,then determined the DNA in a liquid-scintillation.c-fos、c-myc mRNA levels were measured by Northern hybridization.The results were showed by tables.Results The data (Table1,2.3 and 4)Showed the cell number, DNA syhthesis,c-fos mRNA and c-myc mRNA all increased with insulin concentration. There is dose-dependent relationship.Conclusion The results provide that insulin can stimulate the proliferation of vasecular smooth muscle cells and the expression of proto-oncogene c-fos and c-myc.