Abstract: ¬The perinatal period is associated with an increased incidence of thromboembolic complications. Remarkable haemostatic alteration occurred in neonates with severe anoxia and sepsis. The aim of this study is to clarify the impact of critical illness (hypoxia & septicemia) of newborn with elevated liver enzymes (ALT, AST) on the physiologic inhibition system of coagulation including protein C and protein S. Subject and method: we studied 59 critically ill newborns, as well as twenty clinically normal newborns. The 59 ill newborns were classified into group I (hypoxic group) included 27 newborns and group II (septicemic group) included 32 newborns; each group was subdivided according liver enzymes levels to: newborns with normal liver enzymes (group Ia & IIa) and newborns with high liver enzymes›3times normal values (group Ib& IIb). Group III: twenty normal newborns served as control group. Results: In this study protein C& protein S levels were significantly lower in both hypoxic and septicemic newborns with elevated liver enzymes compared to hypoxic and septicemic newborns with normal liver enzymes (P