One hundred fifty-nine cases of hepatocellular carcinomas (HCCs) were reviewed from a series of 1060 cases of percutaneous fine needle biopsies of the liver. The biopsies were performed under ultrasonic guidance using a 22-gauge needle with a beveled tip. Specimens were obtained from the lesion and from areas of normal-appearing liver for comparison. Two sets of slides were prepared for Papanicolaou and Giemsa staining. In 147 cases (92%), the diagnosis of malignancy was established. In 134 cases (84%), the specific diagnosis of HCC was made. Fifty-four percent of the HCCs were well differentiated without cytonuclear abnormalities. In these cases, the diagnosis was made by comparison of specimens from the tumor with those obtained from the normal liver. Thirty-seven percent of the HCC were moderately differentiated with cytonuclear abnormalities. Nine percent of the HCCs were poorly differentiated, and in these cases, identification of glycogen on periodate-Schiff's procedure staining permitted differentiation from a metastatic tumor. In 9 cases, the aspirate was inadequate: there was insufficient tissue in 3 cases and the lesion was missed in the 6 other cases. In 3 cases, a biopsy of normal liver was not obtained and the diagnosis of HCC could only be suspected. Significant bleeding after biopsy occurred in 4 of 1060 cases, all with HCC.