This chapter discusses autonomic dysfunction and hypertension. Behavioral and motivational mechanisms of the brain are regulated at the brainstem level by the limbic system of which the hypothalamus is the key control center. The hypothalamus releases serotonin that has predominantly inhibitory effect on the central vagal nucleus. Serotonin released from the hypothalamus is diencephalic serotonin. Serotonin is also released by raphe nuclei and reticular inhibitory area at medulla. Three main neurotransmitter systems in the brainstem are norepinephrine system, dopamine system and serotonin system explained in this chapter. This chapter also discusses vascular circulatory system and clinical case example.