Portal hypertension usually occurs in patients with fulminant hepatic failure (FHF). There is, however, no information on portal venous hemodynamics in patients with FHF. Therefore, we studied the portal venous hemodynamics in patients with FHF using duplex Doppler ultrasonography. We measured the portal vein diameter, flow velocity, and volume flow with duplex Doppler ultrasonography in 29 patients with FHF and 15 patients with uncomplicated acute viral hepatitis. No significant difference was observed in the portal vein parameters in the two groups. Nineteen patients with FHF survived. No difference in portal flow velocity and flow rate was observed between survivors and nonsurvivors. A significantly lower portal flow velocity was observed in nine patients of FHF with ascites compared with those without ascites (12.29+/-2.81 vs 16.26+/-4.87 cm/sec; P < 0.01). Portal hemodynamics do not significantly change in fulminant hepatic failure; therefore, it has no prognostic significance.