Nonalcoholic fatty liver disease (NAFLD) is an increasingly recognized cause of liver disease in the United States and worldwide. With obesity being an important risk factor universally, NAFLD is now receiving greater attention and is regarded as a public health issue. In addition, as a result of an aging population and the improving control of other major causes of chronic liver disease, such as hepatitis C and hepatitis B, the burden of NAFLD is expected to increase in years to come. Prevalence estimates of this disease vary widely across populations because of differences in methods for diagnosis and/or definition. New strategies for the prevention, diagnosis, and management will be required to alter the course of this disease.