131 patients thought to have diffuse liver disease underwent ultrasonography and percutaneous liver biopsy. The ultrasonographic criteria examined were hepatic echogenicity compared to that of the renal cortex, homogeneity of hepatic parenchyma, and regularity of hepatic outline. On the basis of histologic examination of liver biopsies, several groups of pathologic lesions (not diagnostic entities) were established. Evaluation of ultrasound and histology was double blind. When the lobular architecture of the liver was respected histologically (normal liver, granulomatosis, siderosis, hepatitis), the ultrasound was normal in 86% of cases. The sensitivity of ultrasound was 0.9 for detection of fatty liver and 0.6 for cirrhosis. An abnormal ultrasound predicted structural modifications or a fatty liver in 93% of cases. Ultrasound proved incapable of differentiating between fatty liver and cirrhosis.