Posttraumatic stress disorder (PTSD) involves the onset of psychiatric symptoms after exposure to a traumatic event. PTSD has an estimated lifetime prevalence of 7.8% among adult Americans, and about 15.2% of the men and 8.5% of the women who served in Vietnam suffered from posttraumatic stress disorder (PTSD) > or =15 years after their military service. Physiological responses (increase in heart rate, blood pressure, tremor and other symptoms of autonomic arousal) to reminders of the trauma are a part of the DSM-IV definition of PTSD. Multiple studies have shown that patients suffering from PTSD have increased resting heart rate, increased startle reaction, and increased heart rate and blood pressure as responses to traumatic slides, sounds and scripts. Some researchers have studied the sympathetic nervous system even further by looking at plasma norepinephrine and 24-hour urinary norepinephrine and found them to be elevated in veterans with PTSD as compared to those without PTSD. PTSD is associated with hyperfunctioning of the central noradrenergic system. Hyperactivity of the sympathoadrenal axis might contribute to cardiovascular disease through the effects of the catecholamines on the heart, the vasculature and platelet function. A psychobiological model based on allostatic load has also been proposed and states that chronic stressors over long durations of time lead to increased neuroendocrine responses, which have adverse effects on the body. PTSD has also been shown to be associated with an increased prevalence of substance abuse. With this review, we have discussed the effects of PTSD on the cardiovascular system.