Sepsis and septic shock are systemic responses to infection. Approximately 70% of septic shock cases in humans are caused by a Gram-negative cell wall component, lipopolysaccharide (LPS), also known as endotoxin. Despite significant advances in medical care during the past half century, including the development of numerous potent, broad-spectrum antibiotics, the incidence of sepsis and septic shock has been increasing. The patient populations at greatest risk are growing -- including the immunocompromised, the elderly, and patients within intensive care settings. The incidence of sepsis increased 139% between 1979 and 1987, ranking sepsis as the 13th leading cause of death in the United States, accounting for 50,000 deaths annually. Septic shock portends a poor prognosis, with documented mortality rates up to 77%; it is currently the most common cause of death in US intensive care units.