We performed a cross-sectional study of newly diagnosed cases of nonalcoholic fatty liver disease (NAFLD) identified between December 1998 and December 2000 in the Chronic Liver Disease Surveillance Study. We compared the demographic and clinical features of NAFLD in a racially diverse representative U.S. population (Alameda County, CA). Diagnostic criteria for probable NAFLD were persistent unexplained elevation of serum aminotransferase levels, radiology (ultrasound or computed tomography scan) consistent with fatty liver, and/or two or more of the following: (i) body mass index of 28 kg/m(2) or more, (ii) type 2 diabetes, or (iii) hyperlipidemia, in the absence of significant alcohol use. Definite NAFLD cases required histological confirmation. Of the 742 persons with newly diagnosed chronic liver disease, 159 (21.4%) had definite or probable NAFLD. The majority were nonwhite: Hispanics (28%), Asians (18%), African Americans (3%), and other race(s) (6%). African Americans with NAFLD were significantly older than other racial or ethnic groups (P .001), and in Asians, NAFLD was 3.5 times more common in males than in females (P = .016). Clinical correlates of NAFLD (obesity, hyperlipidemia, diabetes) were similar among racial and ethnic groups, except that body mass index was lower in Asians compared with other groups (P .001). Compared with the base population (Kaiser Permanente members), Hispanics with NAFLD were overrepresented (28% vs. 10%) and whites were underrepresented (45% vs. 59%). In conclusion, these racial and gender variations may reflect differences in genetic susceptibility to visceral adiposity, including hepatic involvement, and may have implications for the evaluation of persons with the metabolic syndrome. Clinicians need to be aware of the variable presentations of NAFLD in different racial and ethnic groups.