['Hepatic steatosis and nonalcoholic steatohepatitis (NASH) have been increasingly implicated in the genesis of hepatic fibrosis and cirrhosis. However, no consensus exists about whether weight reduction may reverse this process.', 'To assess the effect of Roux-en-Y gastric bypass (RYGBP) on the histological evolution of NASH diagnosed in 64 patients by routine liver biopsy ("first" biopsy) performed during surgery, we performed a "second" biopsy after 23.5 +/- 8.4 months in 16 patients (14 female, 2 male).', 'From the first to the second biopsy, BMI decreased from 53.4 +/- 8.8 kg/m2 to 31.1 +/- 4.7 kg/m2, arterial hypertension decreased from 75% to 43.8%, and type 2 diabetes decreased from 43.8% to zero. On the first biopsy, nonalcoholic fatty liver disease (NAFLD) type 3 was observed in 12 patients (75%) and type 4 in 4 (25%). The second biopsy revealed complete regression of NAFLD in 15 patients (93.7%) and only 1 (6.3%) had NAFLD type 1 (mild steatosis without inflammation). Complete regression of necroinflammatory activity was observed in all patients. Among the 4 patients presenting fibrosis in the first biopsy, complete remission was observed in 1 and improvement in 1. Two continued to show the same degree of fibrosis without evidence of disease activity. No worsening of steatosis, necroinflammatory activity or fibrosis was observed in any of the patients, and none progressed to cirrhosis.'] Does roux-en-Y gastric bypass improve the nonalcoholic steatohepatitis ( NASH ) of morbid obesity?