Hypovolemic shock is the most common form of shock seen clinically and has attracted the greatest laboratory interest. It is caused by a sudden decrease in the intravascular blood volume relative to the vascular capacity, to the extent that effective tissue perfusion cannot be maintained. The authors of this article discuss the pathophysiology of hypovolemic shock, the assessment of the patient in shock, the immunologic consequences of shock, impairment of cardiac function in hypovolemic shock, and the management of hypovolemic shock.