Structural changes were examined in liver tissue from 28 patients with chronic bile duct obstruction in whom portal hypertension was diagnosed. Extrahepatic portal occlusion was found in three patients and cirrhosis of the liver in two. In the remaining 23 patients diffuse hepatocyte hyperplasia and portal fibrosis were observed, but a normal spatial relation between portal tracts and hepatic venous radicles was, for the most part, retained. Liver tissue was also examined from a group of 76 patients with chronic bile duct obstruction in whom there was no indication of portal hypertension but some evidence of hepatocyte hyperplasia and fibrosis. Both these features were much less extensive than the changes seen in the group of patients ostensibly suffering from portal hypertension. The findings suggest that the combination of portal hypertension and chronic bile duct obstruction may not imply the unremitting, progressive, and irreversible changes that accompany cirrhosis because the normal vascular relations are retained. In the light of increasing experimental and clinical evidence of the resorption of collagen and the remodelling of hepatic plates it seems that the structural abnormalities in duct obstruction may substantially regress.