Intravascular hemolysis is sometimes harmful and often fatal. Other times it is harmless. Dogs were paired and subjected to hemorrhagic shock. One of the pair was given 2 ml/kg of autologous hemolyzed blood before bleeding. The other of the pair was given 2 ml/kg of heparinized autologous blood. All of the animals given heparinized blood survived, whereas, all of the animals given hemolyzed blood died. The animals given hemolyzed blood developed coagulation changes indicative of Disseminated Intravascular Coagulation (DIC), whereas, the dogs given nonhemolyzed blood did not. It is concluded that hemolysis in the presence of shock (slow capillary flow) causes DIC and death. Hemorrhagic shock alone or hemolysis alone was harmless.