Introduction: Intraperitoneal tumor seeding is a common form of recurrence after surgery for GI tumours. Early diagnosis and treatment may influence the course of disease. Hypothesis and objectives of the work The finding of free tumor cells and / or elevation of tumor markers in peritoneal fluid predicts intraperitoneal tumor recurrence. The results of these tests can be used to indicate HIPEC. Aim of this work is to determine the sensitivity and specificity of cytology and tumor markers levels and importance of these tests for early diagnosis and prognosis of recurrence. Another objective was to confirm the applicability of RT PCR for identification of free tumor cells. Patients and methods . Materials are sourced both during initial surgery (220 patients) and by the dispensary controls (25 patients). The peritoneal fluid was examined cytologically and biochemically too. 50 samples was exemined by RT PCR. Results Elevation of tumor markers or finding of free intraperitoneal tumor cells predicts recurrence. The prognosis of these patients corresponds to stage IV TNM classification, regardless of other parameters TNM. Low sensitivity of these tests (34% for cytology, 53% for tumor markers) does not allow its use as an indicator of HIPEC. Due to degradation of RNA we did not confirm the value of RT...