During severe sepsis, the sustained consumption and/or inhibition of antithrombin leads to a prolonged procoagulant state, which indicates that the administration of antithrombin may be useful in this condition. Animal studies have shown that high doses of antithrombin concentrates can prevent disseminated intravascular coagulation and death. In humans, high doses of antithrombin are required to maintain supranormal antithrombin levels and overcome the magnitude of antithrombin consumption. Three placebo-controlled, double-blind studies of antithrombin concentrates have been performed in France, Germany and northwestern Europe. A meta-analysis of these three studies showed a nonsignificant 22% reduction in 30-day, all-cause mortality. A multicenter phase III trial is needed to demonstrate that antithrombin administration can reduce mortality in septic patients.