The anti-rabbit plasma coagulation factor XIII goat immunoglobulin infusion, prevents the generalized Shwartzman reaction of rabbits elicited by two 24 hours interval intravenous injections of bacterial endotoxin. Measurements of circulating platelets, fibrinogen and factor ?I activities were done after either the first or second injection of endotoxin in both antibody-treated and non-treated rabbits. Twenty four hours after the first injection of endotoxin, a marked increase of platelet was occurred in antibody-treated rabbits, however an increase in fibrinogen was appeared in non-treated ones and forty eight hours after the injection an increase in fibrinogen was greater in antibody-treated group than in non-treated group. Forty eight hours after the first injection of endotoxin, plasma factor ?I activities were decreased in non-treated rabbits. The occurrence of bilateral cortical necrosis was confirmed in four out of five rabbits in non-treated group, whereas no bilateral cortical necrosis was occurred in antibody-treated group.