On the basis of literature review, the structure of the tumor-associated trypsin inhibitor (TATI) marker and its usefulness in diagnosing and monitoring of various malignant neoplasms has been described. The authors' own experiences are presented stemming from evaluation of TATI levels in a group of 305 patients suffering from carcinoma of the uterine body, who were primarily operated and then subjected to supplementary therapy in the Center of Oncology in Warsaw, classified in accordance with the FIGO 1988 protocol in the years 1994-1995, and who were observed for 17 years after discontinuation of treatment. A statistical analysis of the level of the TATI marker was carried out in the group of patients with unfavorable prognostic factors, that is the presence of cancerous infiltration in the uterine body, also found in the parametrium, ovaries, as well as diagnosed metastases to the lymphatic nodes found on the basis of postoperative histopathological protocol. The marker was determined three to seven times in serum after each stage of supplementary treatment, and at the beginning of the follow-up. Strong significance and elevation of the TATI marker were affirmed for the mean of four initial collections in patients, who had a relapse or metastases within one month to 11 years after termination of therapy.