It is well established that obesity increases the risks of hypertension; but the mechanism of this effect is not clear. I will show that leptin elevates blood pressure via action in the dorsomedial nucleus of the hypothalamus, and leptin deficient humans and rodents have lower blood pressure in spite of morbid obesity. Blocking leptin action rapidly reduced blood pressure in obese mice, demonstrating the role that leptin has in the maintenance of cardiovascular functions.