Background Because the mechanisms of the biological effects of statins and angiotensin II type I receptor blocker therapies differ, we studied the vascular responses to these therapies in hypercholesterolemic and hypertensive patients. Methods We administered simvastatin 20 mg and placebo or losartan 100 mg daily during 2 months with washout 2 months to 33 cholesterolemic and hypertensive patients. This study was randomized, double-blind, placebo-controlled, crossover in design. Results Simvastatin alone or losartan combined with simvastatin significantly changed lipoproteins, and improved the percent flow-mediated dilator response (FMD) to hyperemia by 42짹5% and by 75짹5%, respectively (both P<0.001) and reduced serum levels of C-reactive protein (CRP) by 12% and by 17%, respectively (P=0.021 and P=0.003, respectively), compared with baseline measurements. Both therapies did not significantly change the percent nitroglycerin-induced dilator response (NTG). There were no significant correlations between the percent changes in lipoprotein or CRP levels and the percent changes in FMD after each therapy. There were no significant correlations between the percent changes in FMD or CRP levels and the percent changes in blood pressure after each therapy. Of interest, losartan combined with simvastatin changed FMD and CRP levels to greater extent than simvastatin alone (P<0.001 and P=0.501, respectively),. Conclusions Compared with simvastatin alone, added losartan to simvastatin showed additive effects on flow-mediated dilation and inflammation marker in hypercholesterolemic and hypertensive patients.