The objectives are to: (1) characterize ethnic-specific differences in alanine aminotransferase (ALT) elevation among obese children, (2) investigate the earliest ages at which significant ALT elevation occurs, and (3) determine associations between ALT and biochemical parameters. A cohort of 134 multiethnic obese children and adolescents was analyzed retrospectively. ALT levels > or =45 U/L or <45 U/L, denoting high or normal risk, were used to categorize obese children's risk for developing nonalcoholic steatohepatitis. In all, 60% of Hispanics had high-risk ALT levels compared with 12% of whites and 8% of blacks. A significantly higher proportion of boys had ALT > or = 45 U/L (49.4%, vs 37.9% for girls, P = .002); 17.5% were Hispanic boys less than 7 years old. Obese Hispanic children, particularly boys, not only have higher ALT levels but present alarmingly young with high-risk levels. This study highlights a discrete subgroup of children who may present with fatty liver at a younger age and should be screened earlier.