Nonalcoholic steatohepatitis (NASH) may cause progressive hepatic fibrosis, cirrhosis, and hepatocellular carcinoma. Treatment, thus far, has been restricted to diet and weight loss, but without compelling results. In this study we aimed to evaluate the efficacy of orlistat therapy in obese patients with NASH. Fourteen obese patients with NASH underwent liver biopsy prior to and subsequent to 6 months treatment with orlistat (120 mg tid). Hepatic fat extension was graded as normal, mild, moderate, or severe. Hepatic fibrosis was scored on a scale from 0 to 4, with 0 denoting no fibrosis and 4, cirrhosis. Portal inflammation was scored as 0–3, with 0 = normal, 1 = mild, 2 = moderate, and 3 = severe inflammation. Fourteen patients had NASH associated with diabetes, hyperlipidemia, or obesity. Orlistat reduced fatty infiltration in 10 patients (70%; P<0.01), 3 of whom had normal liver fat content after treatment. Orlistat improved inflammatory activity by 2 grades in 28% and by 1 grade in 50% of patients and effected no change in 22% of patients. Five patients (35%) returned to normal inflammatory activity. Orlistat improved hepatic fibrosis by 2 grades in three patients (21%) and by 1 grade in seven patients (50%). There was no change in four patients (28%). Orlistat lowered aminotransferases levels, total cholesterol, triglycerides and low-density lipoprotein, respectively. Insulin resistance index and malonyl dialdehyde levels improved significantly after orlistat therapy, whereas HbAıc remained unchanged. In conclusion, in obese patients with NASH, liver fibrosis and inflammation improved after therapy with orlistat.