Aim To investigate the role of angiotensin Ⅱ receptor antagonist losartan on the protein and mRNA expression of monnocyte chemoattractant protein 1 (MCP 1) in cultured rabbit aortic smooth muscle cells (SMC). Methods The levels of protein and mRNA expression of MCP 1 in cultured SMC and the contents of MCP 1 in the cultured media of SMC were detected by cytochemistry,situ hybridization and enzyme linked immunosorbent assay. Results 10 -6 ～10 -10 mol/L angiotensin Ⅱ(ATⅡ) increased the levels of protein and mRNA expression of MCP 1 in the cultured rabbit aortic SMC in a dose dependent manner and the co)ntents of MCP 1 in the cultured media of of SMC (P<0.001). Losartan markedly reduced the protein and mRNA expression of MCP 1 in the cultured rabbit aortic SMC and the contents of MCP 1 in the cultured media of of SMC induced by ATⅡ. Conclusions Losartan may antagonist ATⅡ induced protein and mRNA expression and secretion of MCP 1 in the cultured rabbit aortic SMC,which might play an important role in preventing the early atherosclerosis and the restenosis after angioplasty.