Two patients with portal hypertension following chronic exposure to vinyl chloride monomer were studied histologically and ultrastructurally. Both cases showed non-cirrhotic portal hypertension accompanied by esophageal varices and splenomegaly. They proved hepatic fibrosis with conventional microscope. Ultrastructurally, there were large amounts of small myelin-like lamellar materials with electron density and remarkable proliferation and vesiculation of smooth endoplasmic reticulum in the cytoplasms of hepatocytes. The widened Disse's spaces, were the sinusoidal lining cells were arranged in multilayers, were plugged by collagenous fiber bundles. The finding may be consistent with the development of portal hypertension.