Experimental evidence suggests that the hypoxic fraction in a solid tumor may increase its malignant potential and reduce its sensitivity towards non-surgical treatment modalities (e.g. standard irradiation, certain anticancer agents). However, the clinical importance of tumor hypoxia remains uncertain since valid methods for the routine measurement of intratumoral O2-tensions in patients have so far been lacking. A clinically applicable standardized procedure has been established which enables the determination of intratumoral oxygen tensions in advanced cervical cancers by use of a computerized polarographic needle electrode histography system. Tumor oxygenation as measured by this method represents a novel tumor feature which can be individually determined for each tumor and which is independent from other known oncological parameters. The results of an interim analysis of an open prospective clinical trial to evaluate the prognostic significance of tumor oxygenation based on the survival data of the first 31 patients are presented. Fifteen patients have been treated by primary radiation, 11 patients received multimodality therapy including irradiation. After a median follow-up of 19 months (range 5-31 months), Kaplan-Meier-life table analysis showed significantly lower survival and recurrence-free survival for patients with a median pO2 of < or = 10 mmHg compared to those with better oxygenated tumors (median pO2 > 10 mmHg). The Cox proportional hazards model revealed that the median pO2 and the clinical stage according to the FIGO are independent, highly significant predictors of survival and recurrence-free survival. We conclude from these preliminary results that tumor oxygenation as determined with this standardized procedure appears to be a new independent prognostic factor influencing survival in advanced cancer of the uterine cervix.