Aim of the study: A  number of ob-

servations have indicated that the immune system plays a significant role in patients with epithelial ovari-an cancer (EOC). In cases of EOC, the prognostic significance of tumour in-filtrating lymphocytes has not been clearly explained yet. The aim is to de-termine the phenotype and activation molecules of cytotoxic T cell and NK cell subpopulations and to compare their representation in malignant as-cites and peripheral blood in patients with ovarian cancer. Material and methods: Cytotoxic cells taken from blood samples of the cu-bital vein and malignant ascites were obtained from 53 patients with EOC. Their surface and activation charac-teristics were determined by means of a flow cytometer. Immunopheno-type multiparametric analysis of pe-ripheral blood lymphocytes (PBLs) and tumour infiltrating lymphocytes (TILs) was carried out. Results: CD3+ T lymphocytes were the main population of TILs (75.9%