The "congestion index" is used to mean the ratio between the cross-sectional area (cm2) and the blood flow velocity (cm/sec) of the portal vein, as determined by a duplex Doppler system. The indices as determined in normal subjects and patients with liver disease were as follows: normal subjects (n = 85), 0.070 +/- 0.029 cm X sec; acute hepatitis (n = 11), 0.071 +/- 0.014 cm X sec; chronic active hepatitis (n = 42) 0.119 +/- 0.084 cm X sec; cirrhosis (n = 72), 0.171 +/- 0.075 cm X sec; and idiopathic portal hypertension (n = 11), 0.180 +/- 0.107 cm X sec. There was a statistically significant difference between the congestion indices from the normal subject group and indices obtained from patients with chronic hepatitis, cirrhosis, and idiopathic portal hypertension. A weak positive correlation was obtained between the congestion index and the portal venous pressure, measured simultaneously through a percutaneously placed catheter (n = 64, r = 0.45, p less than 0.01). It is suggested that the congestion index reflects the pathophysiological hemodynamics of the portal venous system in portal hypertension.