In a study of mesenchymal stem cells (MSCs) to treat atherosclerotic renovascular disease, 28 patients received standard medical treatment, 14 of whom also received a single infusion of MSCs. Patients who received MSCs showed no adverse clinical effects. 3 months after treatment, cortical perfusion and renal blood flow were increased, and tissue fractional hypoxia was decreased, in kidneys from patients treated with MSCs but not in those who received standard therapy. These data indicate that the infusion of MSCs is safe and might be suitable for the treatment of atherosclerotic renovascular disease.