Splenomegaly is a common finding in beta-thalassemia; however, its hemodynamic features and its potential correlations with high output state and hepatic disorders, both also frequent in thalassemia, have not yet been assessed in these patients. Eight beta-thalassemia patients with the indication for splenectomy and no symptoms or signs of heart disease, aged 25.6+/-5.5 years, were studied. Preoperative assessment included hematological profile, liver biology, hepatitis virus serology, and echocardiography. During splenectomy, splenic artery blood flow and splenic vein pressure were directly measured and liver biopsies were taken. Preoperative echocardiographic data were compared with those of 34 healthy controls. The preoperative cardiac index was significantly elevated in patients (4.8+/-1.3 vs 3.4+/-1.1 l/min per m2 in controls, p<0.001). Splenic blood flow, although increased, was not particularly high, being 285+/-56 ml/min or 0.13+/-0.04 ml/min per g of splenic mass, representing 4.1+/-0.9% of total cardiac output (CO). Splenic vein pressure was considerably elevated (29.7+/-5.5 cmH2O). Hepatic fibrosis, iron deposition, and extramedullary foci were found in all eight biopsies. Serology was positive in five of eight cases. beta-thalassemia patients with extensive splenomegaly requiring splenectomy are characterized by high output state, increased splenic blood flow, which probably makes a limited contribution to CO elevation, and portal hypertension, manifest by increased splenic vein pressure and hepatic histopathological abnormalities.