Diffuse congestion of capillaries and venules in visceral areas has been described by Moon1 as the lesion of hemorrhagic shock. Wiggers2 regarded pathologic changes having real bearing on the functional derangements of hemorrhagic shock to be the firmly contracted spleen and distinctive changes in intestinal mucosa; that is, hyperemia, congestion, edema, and petechial hemorrhage. More recently, attention has been focused on acute tubular necrosis, the renal lesion of shock from hemorrhage and injury. Fine3 and others, however, have come to the conclusion that the liver is the locus of the primary defect of irreversible hemorrhagic shock. In the present study histologic observations were made on tissues from dogs subjected to hemorrhagic shock. A hepatic lesion was consistently observed in animals subjected to hemorrhage and transfusion of shed blood. Criteria differentiating the observed lesion from chronic passive congestion or hyperemia are proposed. Methods and Materials Gross and microscopic