Congenital antithrombin III deficiency is an uncommon but important cause of venous thrombosis, usually presenting with recurrent or atypical venous throm boembolism. Its importance lies in the fact that early recognition can lead to treatment in the acute stage, which can prevent propagation of the disease, and further prophylactic treatment may reduce the incidence of further episodes. The authors present a case of mesenteric venous infarction associated with congeni tal antithrombin III deficiency and briefly discuss the diagnosis, surgical impli cations, and treatment of this disorder.