Idiopathic portal hypertension is common in Japan and India but exceedingly rare in Europe and North America. Its pathogenesis remains unelucidated, but may involve phlebosclerosis associated with protein C deficiency or fibrosis upstream from the sinusoids with consequent sinusoid obstruction. Possible etiologic factors include abdominal infections, exposure to toxic substances, and disorders characterized by immune dysfunction. Onset can occur at any age. Digestive bleeding is the presenting manifestation in most instances, although enlargement of the spleen or hematologic disorders are inaugural in some cases. Portography and liver histology (which often requires a surgical biopsy) demonstrate fairly specific venous abnormalities. Bleeding from esophageal varices is the main complication. In the long term, some patients develop liver failure with manifestations similar to those of advanced cirrhosis. The indications of surgery, recently developed decompression procedures (ligations and transjugular intrahepatic portosystemic shunts), and sclerosis are discussed.