Oxygenation of tumor tissue has recently been assed an important prerequisite for the effectiveness of radiotherapy in cervical cancer. Hyperviscosity is a common phenomenon in malignancy and a cause of reduced oxygen transport capacity that would favour tissue hypoxia. Hemorheological variables were serially tested preoperatively, during four cycles of fractionated adjuvant IR192 HDR after loading radiation (HDR-AL) of the vaginal vault (weekly intervals), and 6 months postoperatively in patients with cervical (n=12) and endometrial cancer (n=26). Women who were scheduled for benign tumor surgery served as controls (n=29). Preoperatively, in cervical and endometrial cancer patients, mean plasma viscosity (PV: 1.31±0.1 mPa s; p<0.05; 1.35±0.13 mPa s; p<0.001) and fibrinogen levels (383±46 mg/dL; p<0.05; 379±117 mg/dL; p<0.05) were higher as compared to the controls (1.25±0.07 mPa s; 314±89 mg/dL). Red blood cell aggregation at low shear and stasis (RBC agg.: 15.7±5.6; p<0.05; 29.6±9.1; p<0.05) was higher in endometrial cancer patients as compared to the controls (13.7±3.4; 25.3±5.6). Postoperatively PV decreased in endometrial cancer patients and transiently increased in cervical cancer patients. After the third session of irradiation in both cancer groups, PV regained and at the 6-month checkup, levels were higher as compared to the values before surgery. Postoperatively fibrinogen levels increased and remained higher throughout HDR-AL and 6 months postoperatively. After surgery and during irradiation, anemia persisted in both cancer groups while hematocrit recovered after 6 months in endometrial cancer patients. Thrombosis was diagnosed in three patients postoperatively (7.9 %) but in none during HDR-AL. While a temporary reduction of hyperviscosity is found postoperatively and during HDR-AL in uterine cancer patients, 6 months after surgery RBC aggregation, PV, and hematocrit returned to the pretreatment range.