The beneficial effects of losartan and rosuvastatin on neointimal formation have been well characterized, but little is known about the combined treatment benefit of these two drugs. This study was designed to investigate the synergistic effect of losartan combined with rosuvastatin on the magnitude of protective action in vascular injury mediated by cuff-induced neointimal formation model in vivo. Losartan at 20 mg/kg or rosuvastatin at 40 mg/kg significantly decreased both the neointimal formation and BrdU-positive cells in neointima, indicating the inhibition of cell proliferation including a progress of DNA synthesis. The combination treatment used lower doses of losartan with rosuvastatin (10 + 20 & 5 + 10 mg/kg, respectively) that proved to be significant in decreasing the neointimal formation and BrdU incorporation. These results were comparable to the diminution attained with monotherapy of either drug in higher doses. Interaction index measured by isobolar method indicated drug synergism in these two combinations of both drugs at lower doses. Therefore, the administration of losartan and rosuvastatin in combination with low doses synergistically decreased in cuffinduced neointimal formation by reducing cell proliferation, suggesting that this drug synergism may be fully effective with, lower adverse effects, for the treatment of vascular remodeling such as restenosis.