A significant burn injury is a serious and mortal event. The most important threat to life is hypovolemic shock with complex pathophysiologic mechanisms. Burn depth is classified as first, second, or third degree. Local inflammatory response results a vasodilatation and an increase in vascular permeability. A burn injury is a three dimensional ischemic wound. Zone of coagulation is the zone with maximum damage. Zone of stasis consists of damaged but viable tissues, the tissue is salvageable. In zone of hyperemia tissue perfusion is increased. At the beginning, cardiac output falls and systemic vascular resistance increases; cardiac performance improves as hypovolemia is corrected with fluid resuscitation. While cardiac output increases systemic vascular resistance falls below normal values and a hypermetabolic state develops. Pulmonary vascular resistance increases immediately after thermal injury and this is more prolonged. To avoid secondary pulmonary complications, the smallest resuscitation volume of fluids that maintains adequate tissue perfusion should be given. Changes parallel to the cardiovascular response develop in other organ systems. The reasons of burn injury can be thermal, electrical, chemical or radiation. It is important to know the exact mechanism of burn injury because of different therapies for a specific cause. In this review information about burn depth, local and systemic responses to burn injury and major causes of burn injury are presented.