Glypican-3 is a heparin sulfate proteoglycan normally expressed in fetal liver and placenta, but not in normal adult liver. Preliminary studies have shown that glypican-3 can be useful for the diagnosis of hepatocellular carcinoma. We performed immunohistochemistry for glypican-3 on 80 resection cases of hepatocellular lesions to examine the utility of glypican-3 immunohistochemistry in hepatocellular carcinoma at two ends of the differentiation spectrum. Staining was compared to Hep Par 1 in poorly differentiated cases. Glypican-3 was expressed in 46 (79%) hepatocellular carcinomas (56, 83 and 89% of well, moderately and poorly differentiated respectively) and seven (64%) fibrolamellar carcinomas. Of the 16 well differentiated cases, 10 closely resembled adenoma and were diagnosed due to focal abnormalities and/or loss of reticulin. Glypican-3 expression was seen in 50% in this group. Hepatocellular carcinomas arising in cirrhotic liver were more likely to be glypican-3 positive (91 vs 57%, P=0.004). All hepatic adenomas and macroregenerative nodules were negative, and three (43%) high grade dysplastic nodules were positive. Focal staining was seen in regenerative nodules in four (11%) cirrhosis cases. Glypican-3 was significantly more sensitive than Hep Par 1 for diagnosis of poorly differentiated hepatocellular carcinomas (89 vs 63%, P=0.02). The difference was more significant when only cases with diffuse positive staining were considered (83 vs 21%, P<0.001). In conclusion, glypican-3 has high sensitivity for the diagnosis of hepatocellular carcinoma, but is less sensitive in the extremely well differentiated hepatocellular carcinoma and fibrolamellar variant of hepatocellular carcinoma. Caution should be exercised in using glypican-3 in biopsy specimens as cirrhotic nodules can show strong expression. Glypican-3 can be especially useful in the identification of poorly differentiated hepatocellular carcinoma as it has higher sensitivity compared to Hep Par 1.