Aim To explore the effects of homocysteine(Hcy) on the expression of matrix metalloproteinase-2(MMP-2) in rat vascular smooth muscle cells(VSMC). Methods Cultured rat VSMC was incubated with different concentration of Hcy in vitro for 24,48 and 72 h.The expression of MMP-2 was determined by using the methods of gelatin zymography and western blotting. Results 0.05～1.0 mmol/L Hcy increased the expression of MMP-2 significantly.Incubated with the same concentration of Hcy the level of MMP-2 of 72 h was higher than that of 24 h and 48 h. Hcy >5.0 mmol/L reduced the expression of MMP-2.Incubated with the same concentration of Hcy(>5.0 mmol/L) the level of MMP-2 of 72 h was lower than that of 24 h and 48 h. Conclusions These datas suggested that Hcy can affect the expression of MMP-2 in VSMC.It may be one of factors in the pathogenesis of atherosclerosis induced by Hcy.