Immunotherapy is a potentially attractive treatment option for patients with hepatocellular carcinoma (HCC). We have reported that glypican-3 (GPC3) is an ideal target for anticancer immunotherapy against HCC because its expression is specifically detected in > 80% of HCCs, even during the early stages. Further, increased GPC3 expression is correlated with a poor prognosis. Based on results obtained from a preclinical study using mice, we conducted a phase I clinical trial using a GPC3-derived peptide vaccine. Phase I results showed that the GPC3-derived peptide vaccine was well tolerated. Furthermore, this was the first study to show that the frequency of peptide-specific cytotoxic T lymphocytes was correlated with overall survival in patients with HCC receiving a peptide vaccine. Next, we conducted a phase II clinical trial using the GPC3-derived peptide vaccine in patients with HCC after surgery or radiofrequency ablation (adjuvant setting). We are currently evaluating a third trial involving liver biopsies removed from patients with advanced HCC before and after GPC3-derived peptide vaccination. We expect that the results of these trials will result in future drug development.