Fluid and electrolyte balance in the human organism is controlled by aldosterone, a mineralocorticoid hormone of the suprarenal glands. The major target cells are localized in the kidney where the hormone controls transepithelial salt transport. Over the past few years, evidence has been accumulated that cells of the cardiovascular system are also targeted by the hormone. As an example, endothelial cells resemble similar mechanisms triggered by aldosterone as shown for the kidney. Although the pathological alterations induced by aldosterone excess are obvious, the physiological changes are largely unknown. On the basis of recent experiments, using atomic force microscopy as an imaging tool and a mechanical sensor, I present a hypothesis on the physiological role of aldosterone in endothelial function and its potential implications in the control of blood pressure.