Magnetic resonance signal intensity of focal liver lesions is affected by numerous pathologic factors. Lesion histologic features, such as cellularity, vascularity, stromal component, and intratumoral necrosis or hemorrhage, strongly affect T1 and T2 relaxation times. Additionally, intracellular content of certain substances, such as glycogen, fat, melanin, iron, and copper, may also have a substantial role in determining MR signal behavior. In this review we discuss the correlations between MR imaging features and pathologic findings in benign and malignant focal liver lesions. Knowledge of imaging-pathology correlations greatly assist in charac terizing focal lesions. Moreover, in certain tumor histotypes, such as hepatocellular carcinoma, careful analysis of lesion signal intensity may help predict the degree of tumor differentiation.