Severe sepsis is a common cause of mortality and morbidity in intensive care unit, and when associated with shock is more series. The objective of our study was to determine the role of a new marker which might be used as a specific (decisive) and I or non specific indicator of the inflammatory response, also to detect its ability to segregate patients at high risk and see their outcome and prognosis.The material of our study included 50 cases subdivided into 3 groups:The first group comprised 20 patients (40 %) who developed septic shock on / *or immediately after admission to the critical care center, Cairo University Hospital.The second group comprised 10 patients (20%) with sepsis whatever the cause is.The third group comprised 20 healthy subjects (40%) serving a control group.Besides personal and medical history, clinical examination, 12 lead ECG, chest X-ray, routine laboratory investigations as: ABG, complete blood picture, blood sugar, renal and liver profiles, electrolytes and coagulation profiles ,were performed. In addition serial samples were withdrawn on admission, third and seventh days during hospital course for polymorphonuclear elastase (PMN) enzyme measurement.Our results had shown a statistically increased levels of PMN elastase enzyme in group one and group two as compared to control group (P <0.000001, P < 0.001) respectively; but there was no significant difference between group one as compared to group two (P <0.6).We can conclude that PMN elastase as an indicator of inflammatory response together with other indicators might help to identify patients at risk determining their outcome and prognosis.