The diagnostic value of glypican 3 (GPC3) immunostaining on needle biopsy specimens has not been well assessed. In this study, 120 liver needle biopsy specimens, including 46 from cirrhotic livers and 74 hepatocellular carcinomas (HCCs), were immunohistochemically examined for expression of GPC3. The results showed strong cytoplasmic and membranous staining in 36 HCCs (49%), among which 20 cases (56%) showed diffuse immunoreactivity. None of the 46 cirrhotic livers exhibited positive GPC3 immunostaining. The nonneoplastic liver tissues (cirrhotic or noncirrhotic) that were present in the majority of the HCC cases were also completely negative for GPC3 expression. These data demonstrate that GPC3 is a reliable immunohistochemical marker for the diagnosis of HCC on needle biopsy specimens when positive. However, the detection rate in our series seems lower than that reported in studies using resection specimens as the study materials. Our findings emphasize that GPC3 immunoreactivity can be focal and that negative staining should not be viewed as evidence to exclude the diagnosis of HCC in challenging needle biopsy specimens.