Updated project metadata. BACKGROUND. For developing targeted immunotherapy against ovarian adenocarcinoma, direct identification of peptides presented by major histocompatibility complex class I (HLA I) on the surface of tumor cells can be utilized. AIM. To identify ligands of HLA I of ovarian adenocarcinoma tumors. METHODS. Immunopeptidome from postoperative material of patients with ovarian adenocarcinoma were isolated using immunoaffinity chromatography and analyzed by liquid chromatography-mass spectrometry. RESULTS. Using NP-40, 5 peptides belonging to the proteins of cancer/testis antigens (CTA) were identified in the immunopeptidomes of postoperative material from patients with ovarian adenocarcinoma, 3 of which, according to the human protein atlas, are indeed not expressed in normal ovarian tissues. CONCLUSION. Immunopeptidome analysis allows the identification of peptides of CTA proteins, but a larger sample of postoperative material from patients with ovarian adenocarcinoma and experimental testing of the immunogenicity of the identified peptides are needed for further research.