Nonalcoholic fatty liver disease is a clinicopathologic syndrome that encompasses several clinical entities. The spectrum of conditions ranges from simple steatosis to steatohepatitis, fibrosis and end stage liver disease. The condition was originally described in obese, diabetic, middle-aged females without a history of significant alcohol use with liver histology consistent with alcoholic hepatitis. It is known that this entity occurs without any particular sex predilection, in lean individuals, as well as an increasing number of obese children. Other terms have been used to describe this clinical entity such as alcohol-like hepatitis, pseudo-alcoholic hepatitis, diabetic hepatitis and steatonecrosis. Ludwig and colleagues introduced the term nonalcoholic steatohepatitis (NASH) to describe patients fitting the picture of alcoholic hepatitis but without a history of significant alcohol abuse. The term nonalcoholic fatty liver disease (NAFLD) is used more frequently to include the spectrum of conditions that range from steatosis through steatohepatitis, fibrosis and cirrhosis. NASH is reserved for patients with steatohepatitis and fibrosis. NAFLD is now being recognized as the most common cause of elevated liver enzymes in the United States. Although the exact etiology of NAFLD is not known, it may be caused by insulin resistance coupled with increased oxidative stress to the hepatocytes. No specific therapy has been approved for this condition and the mainstay of management is weight loss.