To verify the value of ultrasound (US) in the diagnosis of cirrhosis, the ratio of transverse caudate lobe width to right lobe width (C/RL) was determined with US in 25 healthy subjects and 156 consecutive patients with either histologically proved acute viral, chronic persistent, or chronic active hepatitis or cirrhosis. The C/RL ratio had a sensitivity of 43%, a specificity of 100%, and an accuracy of 79% in cirrhosis. The sensitivity was very low in alcoholic cirrhosis, low in cryptogenic cirrhosis, and high in hepatitis B virus related cirrhosis. In spite of its fairly low overall sensitivity, the C/RL ratio is a useful measurement in assessing chronic liver disease because of its high specificity in cirrhosis.