Backoround Hepatocellular carcinoma （HCC） often occurs in association with liver cirrhosis. A stepwise carcinogenesis for HCC has been proposed. The purpose of this study was to observe the enhancement pattern of hepatocellular nodules in cirrhotic patients using contrast-enhanced ultrasound （CEUS） and to correlate patterns of enhancement at CEUS with the diagnosis of hepatocellular nodules using pathologic correlation as the gold standard. Methods Ninety-three cirrhotic patients with indeterminate hepatocellular nodules at ultrasound, underwent biopsy of each indeterminate nodule. Patients with nodules found to have pathologic diagnoses of regenerative nodules （RNs）, dysplastic nodules （DNs）, or DNs with focus of HCC （DN-HCC）, were enrolled in this study. Enhancement patterns of all nodules were examined throughout the various vascular phases of CEUS and classified into five enhancement patterns： type I, isoenhancement to hepatic parenchyma at all phases; type II, hypoenhancement in the arterial phase, and isoenhancement in the portal venous phase and late phase; type III, iso-to-hypoenhancement in arterial and portal venous phase, and hypoenhancement in the late phase （washout）; type IV, slight hyperenhancement in the arterial and portal venous phase and hypoenhancement in the late phase （washout）; and type V, partial hyperenhancement in the arterial phase and hypoenhancement in the late phase; and another partial iso-to-hypoenhancement in the arterial and portal venous phase and hypoenhancement in the late phase （washout）. The correlation between the contrast enhancement patterns and the pathological diagnoses was analyzed by the chi-squared test. Results Totally 132 lesions were examined with CEUS in 93 patients. Pathologic diagnoses included 45 DN, 68 RN, and 19 DN-HCC. The enhancement patterns observed were as follows： type I, 49 （37.1%）; type II, 27 （20.5%）; type III, 28 （21.2%）; type IV, 9 （6.8%）; type V, 19 （14.4%）. Nodules with type I enhancement s
