Leptin(LP) secreted mainly from adipocyte and regulated by the obese gene,regulates food intake and body weight balance through die central and peripheral nervous system. On the other hand, LP involves the patho-physiologic effect of immune response, anti-inflammatory process and tissue repairing in trauma. In newly findings,LP may inhibit the activation and necrosis of the neutrophil and monocyte.and LP may play an important role in protecting the organ function in severe cases. In severe infection, the change of LP level may be a clue in evaluating prognosis of sepsis and septic shock. This article reviews the expression of LP,and the relationship between the LP and major cytokines in severe sepsis and septic shock.