Background: The object of this study was to investigate the safety and clinical response of immunotherapy targeting the WT1 (Wilms' tumor 1) gene product in patients with gynecological cancer. Patients and Methods: Twelve patients with WT1/human leukocyte antigen (HLA)-A*2402-positive gynecological cancer were included in a Phase II clinical trial of WT1 vaccine therapy. In all the patients, the tumors were resistant to standard therapy. The patients received intradermal injections of a HLA-A*2402-restricted, modified 9-mer WTI peptide every week for 12 weeks. Tumor size, which was measured by computed tomography (CT), was determined ever), 4 weeks. The responses were analyzed according to Response Evaluation Criteria in Solid Tumors (RECIST). Results: The protocol was well tolerated; only local erythema occurred at the WTI vaccine injection site. The clinical responses were as follows: stable disease (SD) in 3 patients and progressive disease (PD) in 9 patients. No patients had a complete (CR) or partial response (PR). The disease control rate was 25.0%. Conclusion: Although a small, uncontrolled, nonrandomized trial, this study showed that WT1 vaccine therapy for patients with gynecological cancer was safe and produced a clinical response.