Forty-seven consecutive patients were prospectively evaluated to study the incidence of hepatic encephalopathy as well as modifications in the PSE index after TIPS. Various clinical, laboratory, and angiographic parameters were also recorded to identify risk factors for the development of post-TIPS hepatic encephalopathy (HE). Mean follow-up was 17 +/- 7 months. During follow-up, six patients died and one underwent transplantation. All other patients were followed for at least a year. Fifteen patients (32%) experienced 20 acute episodes of precipitated HE (hospitalization was necessary in 10 instances), and five patients (11%) presented a continuous alteration in mental status with frequent spontaneous exacerbation during follow-up. Both precipitated and spontaneous HE occurred more frequently during the first three months of follow-up. Moreover the PSE index was significantly worse than basal values one month after TIPS, thereafter returning to near basal values. HE was successfully treated in all patients but one who required a reduction in the stent/shunt diameter. Increasing age (>65 years) and low portacaval gradient (<10 mm Hg) were predictors of HE after TIPS. A gradual dilation of the stent/shunt should be performed to obtain a portacaval gradient >10 mm Hg to avoid an unacceptable rate of HE after TIPS.