Nonalcoholic fatty liver disease (NAFLD) is an increasingly recognized medical condition that may progress to hepatic cirrhosis with liver failure. The pathologic picture resembles that of alcohol-induced liver injury, but it occurs in patients who do not abuse alcohol. NAFLD is more common among patients with evidence of insulin resistance. NAFLD refers to a wide spectrum of liver damage, ranging from simple steatosis to steatohepatitis, fibrosis, and cirrhosis. The clinical implications of NAFLD are derived mostly from its common occurrence in the general population, specifically in obese individuals, and its potential to progress to cirrhosis and liver failure. It is difficult to propose a treatment strategy for NAFLD because its pathogenesis is poorly understood; however, the most commonly associated clinical features of obesity, diabetes mellitus, lipid disorders, and hypertension deserve therapeutic interventions independent of NAFLD. It is also not known if and how treatment of these other conditions affects the natural history of NAFLD, particularly in the long term.