Despite the increasing prevalence of nonalcoholic fatty liver disease (NAFLD), its pathogenesis and clinical significance remain poorly defined. In this study, we examined and compared the distribution of hepatic triglyceride content (HTGC) in 2,287 subjects from a multiethnic, population-based sample (32.1%white, 48.3%black, and 17.5%Hispanic) using proton magnetic resonance spectroscopy. HTGC varied over a wide range (0.0%-41.7%; median, 3.6%) in the population. Almost one third of the population had hepatic steatosis, and most subjects with hepatic steatosis had normal levels of serum alanine aminotransferase (79%). The frequency of hepatic steatosis varied significantly with ethnicity (45%in Hispanics; 33%in whites; 24%in blacks) and sex (42%in white men; 24%in white women). The higher prevalence of hepatic steatosis in Hispanics was due to the higher prevalence of obesity and insulin resistance in this ethnic group. However, the lower frequency of hepatic steatosis in blacks was not explained by ethnic differences in body mass index, insulin resistance, ethanol ingestion, or medication use. The prevalence of hepatic steatosis was greater in men than women among whites, but not in blacks or Hispanics. The ethnic differences in the frequency of hepatic steatosis in this study mirror those observed previously for NAFLD-related cirrhosis (Hispanics >whites >blacks). In conclusion, the significant ethnic and sex differences in the prevalence of hepatic steatosis documented in this study may have a profound impact on susceptibility to steatosis-related liver disease. Despite this increasing prevalence of nonalcoholic fatty liver disease (NAFLD), its pathogenesis and clinical significance remain poorly defined. In this study, we examined and compared the distribution of hepatic triglyceride content (HTGC) in 2,287 subjects from a multiethnic, population-based sample (32.1% white, 48.3% black, and 17.5% Hispanic) using proton magnetic resonance spectroscopy. HTGC varied over a wide range (0.0% -41.7%; median, 3.6%) in the population. Almost one third of the population had hepatic steatosis, and most subjects with hepatic steatosis had normal levels of serum alanine aminotransferase (79%). The frequency of hepatic steatosis varied significantly with ethnicity (45% in Hispanics; 33% in whites; 24% in blacks) and sex in white men; 24% in white women). The higher prevalence of hepatic steatosis in Hispanics was due to the higher prevalence of obesity and insulin resistance in this ethnic group. However, the lower frequency of hepatic steatosis in blacks was n ot explained by ethnic differences in body mass index, insulin resistance, ethanol ingestion, or useable. The prevalence of hepatic steatosis was greater in men than women among whites, but not in blacks or Hispanics. The ethnic differences in the frequency of hepatic steatosis in this study mirror those seen only for NAFLD-related cirrhosis (Hispanics> whites> blacks). In conclusion, the significant ethnic and sex differences in the prevalence of hepatic steatosis documented in this study may have a profound impact on susceptibility to steatosis-related liver disease.