Effects of Hageman factor fragment (factor XIIf) administration on shock induction were studied in anesthetized male Wistar rats with hemorrhagic shock. Administration of factor XIIf in non-hemorrhaged rats resulted in an immediate decrease of mean arterial pressure (MAP) for 5 min and in significant increases of blood glucose, lactate and hematocrit (Hct) as well as in a strong tendency for plasma kallikreinogen (KKN) to decrease. At the beginning of bleeding (15 min after factor XIIf administration) MAP has been normalized again. During subsequent hemorrhage pretreated rats showed a sharper decrease in MAP which remained significantly lower up to 25% of estimated blood volume (EBV) and recovered more slowly to normal level after hemorrhage. Blood glucose, lactate and Hct were significantly higher in pretreated animals after hemorrhage of 30% EBV. KKN depicted significant lower values during hemorrhage and in the posthemorrhagic period. Mortality within the observation time increased from 20% (control group) to 60% (pretreated animals). The results demonstrate that prehemorrhagic kallikrein-kinin system (KKS) activation induced an increased severity of shock state with higher mortality.