Hepatic steatosis is traditionally regarded as a benign condition. In recent years it has been recognized that fatty liver may evolve into a severe form called nonalcoholic steatohepatitis. This term was used first time in 1980 by Ludwig. The pathogenesis of nonalcoholic steatohepatitis is multifactorial. Insulin resistance is thought to be pivotal in the development of steatosis with a subsequent development of oxidative stress and lipidperoxidation. Liver biopsy is a gold standard for the disease diagnosis and prognosis. The reatment is aimed at body weight reduction and the treatment of comorbidities. In the treatment there are administered cytoprotectives - hepatic drugs, antioxidants, antidiabetic drugs, insulin-sensitizing, and antihyperlipidemic agents. However, the effect of the treatment is uncertain.