Background : Biglycan , extracellular matrix proteoglycan of vascular wall, is prominent in the fibrous cap and SMC rich region of atherosclerotic lesion and abundantly accumulated in restenotic lesion. The role of biglycan in vascular physiology and disease still remain a mystery. Objective & Method : To determine the effect of biglycan and glycosaminoglycan deficient biglycan (GDB) overexpression on arterial wall, we observed the extracellular matrix production of retrovirally overexpressed vascular smooth muscle cell(VSMC) in vitro and injured neointima after delivery of overexpressed cells Result : Transgene and transgenic protein of biglycan and GDB in VSMC were confirmed by Northern blot analysis and Western blot analysis. Overexpression of biglycan shows little effects on elastic fiber and collagen fiber production. However, overexpression of GDB show remarkably increased the level of tropoelastin m RNA and prominent accumulation of tropoelastin protein in cell culture and neointima following injury. Overexpression of GAG deficient biglycan also shows decreased expression of collagen a (type I) mRNA and decreased accumulation of collagen fiber type I in cell culture and neointima following injury. Conclusion : These result indicated that the GAG attached to biglycan core protein has critical role in its effects on ECM production and might be a candidate to modify ECM component in vasculature on purpose of decreasing fibrosis