['Endothelium-derived molecules may be predictive to organ injury. Heat shock protein (HSP) A12B is mainly located in endothelial cells, which can be detected in the plasma of septic patients. Whether it is correlated with prognosis of sepsis remains unclear.', 'Extracellular HSPA12B (eHSPA12B) was determined in plasma of septic mice at 6 h, 12 h, 24 h and 48 h after cecal ligation and puncture (CLP). It was also detected in plasma of patients with severe sepsis, sepsis, systemic inflammatory response syndrome and healthy volunteers. The predictive value for prognosis of severe sepsis was assessed by receiver operating curve (ROC) and Cox regression analyses.', 'eHSPA12B was elevated in plasma of CLP mice at 6 h and peaked at 24 h after surgery. A total of 118 subjects were included in the clinical section, including 66 patients with severe sepsis, 21 patients with sepsis, 16 patients with SIRS and 15 volunteers. Plasma eHSPA12B was significantly higher in patients with severe sepsis than in patients with sepsis, SIRS and volunteers. The level of eHSPA12B was also higher in non-survivals than survivals with severe sepsis. The area under the curve (AUC) of eHSPA12B in predicting death among patients with severe sepsis was 0.782 (0.654-0.909) in ROC analysis, much higher than that of IL-6 and IL-10. Cox regression analysis showed that cardiovascular diseases, IL-6 and eHSPA12B were risk factors for mortality in patients with severe sepsis. Survival curve demonstrated a strikingly significant difference between 28-day survival rates of patients with an eHSPA12B lower or not lower than 1.466 ng/ml.'] Is plasma HSPA12B a potential predictor for poor outcome in severe sepsis?