Idiopathic portal hypertension (IPH), so called Banti's disease, is characterized by anemia, splenomegaly and portal hypertension. While sharing certain clinical features, IPH is distinct from liver cirrhosis not only in histopathology and natural history but also in vascular anatomy and portal hemodynamics. Our studies have shown that the majority of patients with IPH have high serum levels of immunoglobulins, including autoantibodies, associated with abnormally high frequencies of activated T cells and the biased usage of particular T cell receptor (TCR) V beta gene segments. These results suggested that IPH was an immunological disorder mediated by a continuous stimulation with either a certain antigen or more likely a superantigen.