Aim The effect of confluent endothelial cell conditioned medium on the proliferation of cultured smooth muscle cells was studied in this article.Methods The conditioned medium of human umbilical vein endothelial cells (hUVEC-CM)was collected and fractionated into 3 fractions:namely A,containing proteoheparan sulfate,proteodermatan sulfate (DSPG) and proteochondroitin-dermatan sulfate(CSDSPG ),B(containing HSPG)and C(containing DSPG and CS-D8PG),by DEAE-Sephacelion -exchange chromatography with NaCl grabient elution.Effect of hUVEC-CM on cultured humanaortic smooth muscle cell(hASMC)proliferation was studied by cell count and 3H-TdR incorporation.Results All 3 fractions of hUVEC-CM could inhibit hASMC proliferation,but the percentages of inhibition were in the order of B>A>C.Conclusion HSPG is the major component of hUVEC-CM in the inhibition of hASMC growth.