Viral hepatitis causes fibrosis in liver and may change liver's mechanical properties. To evaluate the impact of fibrosis on elastic properties of human liver and to investigate potential benefits of ultrasonic elasticity imaging, nineteen fresh human liver samples and one hepatic tumor (focal nodular hyperplasia) sample obtained during operations were studied. Simple ID estimates based on the cyclic compression-relaxation method were preformed. Young's modulus values were derived from the pre-determined strain (controlled by a step motor system) and the stress values (measured by an electronic balance). Each specimen subsequently received histological examination and a grade of liver fibrosis was scored from 0 to 5. Results show that the Young's modulus values were at the order of several hundreds to thousands Pascals. The Young's modulus generally increased with the fibrosis grade though some discrepancies existed at the middle grades of fibrosis (score 1-3). The correlation between the fibrosis score and the Young's modulus was significant (P
