The present study was undertaken to investigate the diagnostic usefulness of fine-needle aspiration biopsy (FNAB) in a large series of patients with hepatocellular carcinoma (HCC) seen over a 1-year period. During 1986, ultrasonographically guided percutaneous FNAB was performed in 72 patients with suspected HCC. A final diagnosis of HCC was made in 58 patients. The presence or absence of HCC was ascertained by histological examination and/or by other diagnostic procedures (alpha 1-fetoprotein, computed tomography, arteriography) and by clinical follow-up (repeated ultrasonographic controls) and/or by surgery or necropsy. A total of 61 FNABs were carried out in these 58 patients. Only 42 (69%) of the 61 FNABs allowed the diagnosis of HCC. This moderate diagnostic sensitivity was not related to tumor size. Only one false positive result was observed in the non-HCC group. Therefore, the diagnostic specificity of FNAB for HCC was 93%, with a positive predictive value of 97% and a negative predictive value of 40%. These results show that FNAB is a useful diagnostic technique in patients with HCC. However, these data also show that there is a large proportion (31%) of subjects with false negative results. Therefore, we suggest that further efforts should be made to improve the diagnostic accuracy of this procedure.