Doppler-duplex has been widely used to quantify blood flow. Nevertheless, its usefulness in assessing portal vein flow (PVF) has been questioned due to technical problems: vessel cross sectional area measurements, interobserver variability, and PVF changes related to physiological events. This study was aimed to measure PVF in patients with cirrhosis and portal hypertension, to estimate changes in PVF during the respiratory cycle, and to evaluate intraobserver variability of Doppler-duplex technique. Twenty-two patients with liver cirrhosis and portal hypertension and 22 healthy subjects were included. One operator made 6 measurements of portal vein diameter (D) and mean flow velocity in inspiration and aspiration. Area of the vessel (A) and PVF were calculated by a microprocessor. Interobserver variability was estimated for each subject and a mean was determined for each group. In the control group, PVF was 901 +/- 39 ml/min in inspiration and 633 +/- 38 ml/min in aspiration; p < 0.001. In patients with cirrhosis PVF was 1303 +/- 121 ml/min in inspiration and 1003 +/- 96 ml/min in aspiration; p < 0.001. Intraobserver variability was 6.0 +/- 0.6% for D, 12.0 +/- 3% for MV and 18.3 +/- 1.6% for PVF in healthy subjects and 5.3 +/- 0.7% for D, 9.2 +/- 0.9% for MV and 15.2 +/- 1.5% for PVF in patients with cirrhosis and portal hypertension. In conclusion, PVF is significantly increased in cirrhotics. PVF was higher in inspiration than espiration in both groups. The Doppler-duplex method evaluation of PVF has an important intraobserver variability (18.3 +/- 1.6%). Then, changes in PVF less than 20% are not accurately measured by this technique.