The study expands upon the findings of the Dietary Approaches to Stop Hypertension (DASH) study, which showed that a dietary pattern emphasizing fruits, vegetables, and low fat dairy products and overall reduced in total and saturated fat significantly lowers blood pressure (BP). The DASH diet is particularly effective in African Americans and in individuals with systolic hypertension. However, it is not known if the DASH diet affects the pathophysiology of the hypertensive process. Preliminary data support the possibility that the DASH diet interrupts the renin-angiotensin system. This raises the intriguing possibility that the DASH diet will favorably impact on cardiovascular and renal hemodynamics in patients with isolated systolic hypertension. Therefore, the central hypothesis of this study is that the DASH diet affects central aortic stiffness, diastolic relaxation, and renal and vascular reactivity to angiotensin II (Ang II) by lowering tissue renin-angiotensin system activity.