To evaluate the accuracy of ultrasonography in diagnosing fatty infiltration of the liver (FIL), the authors compared gray-scale B-mode ultrasonography and unenhanced computed tomographic (CT) liver images in a study of 47 patients. The CT scans, which served as the diagnostic standard, were classified as normal, Grade 1 (mild FIL), Grade 2 (moderate FIL), and Grade 3 (severe FIL). Applying predetermined sonographic textural criteria, two experienced radiologists independently graded each ultrasound study for the presence and severity of FIL. The overall accuracy of ultrasonography in detecting FIL was 85 per cent, with 100 per cent sensitivity and 56 per cent specificity. The sonographic/CT correlation in grading the severity of FIL was particularly good for Grade 2 and Grade 3 FIL. Ultrasound is a sensitive and reasonably accurate diagnostic tool in assessing fatty infiltration of the liver.