The aim of this study was to determine the diagnostic performance of ultrasound (US) in the quantitative assessment of steatosis by comparison with proton magnetic resonance spectroscopy ((1)H-MRS) as a reference standard. Three liver echo-intensity indices were derived: US hepatic mean gray level, hepatic-renal echo-intensity ratio (H/R), and hepatic-portal blood echo-intensity ratio. The (1)H-MRS degree of steatosis was determined as percentage fat by wet weight. Regression equations were used to estimate quantitatively hepatic fat content. The hepatic fat content by (1)H-MRS analysis ranged from 0.10% to 28.9% (median value, 4.8%). Ultrasound H/R was correlated with the degree of steatosis on (1)H-MRS (R(2)= 0.92; P < .0001), whereas no correlation with (1)H-MRS was found for hepatic mean gray level and hepatic-portal blood echo-intensity ratio. A receiver operating characteristic curve identified the H/R of 2.2 as the best cutoff point for the prediction of (1)H-MRS of at least 5%, yielding measures of sensitivity and specificity of 100% and 95%, respectively. In this pilot study, US H/R exhibits high sensitivity and specificity for detecting liver fatty changes. Our results indicate that quantitative evaluation of hepatic fat content can be performed using US H/R and could therefore be a valuable analytic tool in clinical investigation.