For transferable and immunologieal studies on shock toxin (lethal faetor), a hind limbs ischemia tourniquet shock in rats has been examined. The blood of rats subjectd to severe shock transfused into mild shock rats has not significantly increased the mortality of the latter. Both the recruited plasma from shock rats and the plasma from the rats immunized with severe shork plasma had no therapeutic effects on tourniquet shock. It therefore appears that there is no specific and immunogenic shock toxin produced in the tourniquet shock in rats