Three hundred ninety-five consecutive patients with sonographically detected hepatic lesions < or = 3 cm in diameter were submitted to ultrasonically guided fine-needle biopsy: 24 (6.1%) were < or = 1 cm in diameter; 142 (36%) were between 1.1 and 2 cm, and 229 (57.9%) were between 2.1 and 3 cm in diameter. In the 385 controlled cases, we obtained a cytohistological diagnosis of malignancy in 243 (63.1%): 135 hepatocellular carcinomas, 97 metastases, and 11 hepatic lymphomas. There were 104 true negatives (27%) and 38 false negatives (9.9%). The sensitivity of ultrasonically guided fine needle biopsy in the total series was 86.5%, the specificity 100%, with an overall accuracy of 90.1%. The overall accuracy was higher for lesions between 2.1 and 3 cm in diameter (90%) and was lower for lesions located in the sixth segment (84.6%). The correct diagnosis was obtained in the 83.3% (135/162) of small hepatocellular carcinomas versus 89.8% (97/108) in cases of small metastatic lesions.