The purpose of this study was to compare ultrasound with a clinical and biological score to differentiate benign and malignant liver lesions. The study was carried out prospectively in 100 consecutive patients with liver masses of unknown origin. The accuracy of ultrasound and the score was 84% and 76%, respectively (P = 0.02). Ultrasound and the score gave the same results for the diagnosis of hepatic lesions in 68% of cases. When both ultrasound and the score were in agreement, the prediction of malignancy was 94% ant that of benignity was 100% accurate. Although ultrasound was superior to the score in this series, it is interesting to calculate the score because of the higher predictive values when both methods are associated.