Non alcoholic fatty liver diseases (NAFLD) is a clinicopathological entity that encompasses simple steatosis, necroinflammation known as non alcoholic steatohepatitis (NASH) with or without fibrosis. It is strongly associated with the metabolic syndrome. NAFLD is by far the most common cause of liver disease. Key issues in the diagnosis of patients with NAFLD are the differentiation of NASH from simple steatosis and the degree of liver fibrosis. Patients with NASH are at greatest risk of developing complications of chronic liver disease, such as hepatocellular carcinoma even in the absence of cirrhosis. Liver biopsy, which is the gold standard diagnostic method, cannot be proposedfor all patients, given the risk of this procedure and the prevalence of NAFLD. There are some noninvasive scoring systems to find out whether patients have advanced hepatic fibrosis. Knowledge about the interaction between the intestinal microbiota in obesity has rapidly increased in the past few years. Several lines of evidence suggest a role for the gut microbiota in the pathogenesis of NAFLD. Dysbiosis, i.e. imbalance of the intestinal microbiome, may have a role in the progression of NAFLD. At the present time, there are limited treatment options wich include lifestyle modification to lose weight, treatment of the disorders included in the metabolic syndrome and different therapeutic agents. However results are disappointing concerning liver inflammation and fibrosis. Manipulating the gut microbiota may represent a new strategy for patients with NAFLD.