Nonalcoholic fatty liver disease (NAFLD) covers the spectrum of features found in liver laden with macrovesicular fat and variable degrees of inflammation, cell injury, and fibrosis. By definition, NAFLD excludes those with significant ingestion of alcohol or alternative potential cause of steatohepatitis. NAFLD develops with rare exception in children who are obese. Given the rapid rise in prevalence of obesity in children globally, NAFLD is now recognized as the most common cause of liver disease in pediatrics. In obese individuals, Hispanic ethnicity and male gender appear to increase risk. Recent studies suggest that insulin resistance and oxidative stress are important in pathogenesis. Treatment trials are underway to determine if reduction of insulin resistance or oxidative stress will favorably affect outcome. This review summarizes what is known about pediatric nonalcoholic steatohepatitis in terms of prevalence, demographics, clinical presentation, histology,pathogenesis, and treatment. Important differences between pediatric and adult fatty liver disease are highlighted.