Morphological changes of the liver were studied in 24 autopsy cases of noncirrhotic portal hypertension of unknown etiology (idiopathic portal hypertension, IPH), and in 123 surgical biopsies from such patients. For comparison, 15 whole-cut liver slices from autopsy cases of noncirrhotic portal fibrosis (NCPF) from India were also studied. Liver pathology was very similar in IPH and NCPF, characterized by phlebosclerotic changes and perivascular fibrosis of the portal vein system, and parenchymal atrophy perhaps secondary to portal circulatory insufficiency. The distribution of lesions was uneven, and despite marked fibrosis and occasional surface nodularity, there was no diffuse pseudonodule formation in the parenchyma. Surgical specimens showed similar changes except for more frequent portal cellular infiltrates, but the changes seen in one biopsy specimen were limited and not always diagnostic. It seems that IPH of Japan and NCPF of India are the same disease, and perhaps hepatoportal sclerosis elsewhere is also the same disease.