Using an ultrasonic Doppler system, we prospectively studied the changes in portal venous flow (PVF) following percutaneous transhepatic biliary drainage (PTBD) and evaluated the correlation between PVF and liver function in 10 patients with obstructive jaundice. The patients were divided into two groups according to their rate of decrease in serum bilirubin ("b"). Group A comprised 5 patients with a "b" of less than -0.1, while group B consisted of 5 patients who did not meet this criterion. The mean PVF increased following PTBD (P < 0.01). The increase in PVF was due to an increase in the maximum velocity of the portal vein (Vmax). The rate of increase in the Vmax in group A was significantly higher than that in group B on both the 7th and 14th postdrainage days (P < 0.05). The rate of increase in the Vmax correlated significantly with the rate of decrease in the serum bilirubin concentration (P < 0.01). Based on the above findings, we conclude that measuring the Vmax by Doppler ultrasonography is useful in evaluating the liver function in patients with obstructive jaundice.