Introduction: Tissue type assignment, i.e. differentiation tumour from normal tissue, is a normal procedure for interstitial thermometry. In our department, thermometry in patients with a tumour in the lower pelvis is usually restricted to the intra-luminal tracks. It is unknown whether discrimination between normal and tumour tissue is relevant for deep regional hyperthermia thermal dosimetry using only intra-luminal tumour contact and tumour adjacent thermometry. This study has analysed the acquired temperature data in order to answer this question. Patients and methods: Seventy-five patients with locally advanced cervical carcinoma were selected randomly. Patients were treated with a two or three modality combination, i.e. radiotherapy + hyperthermia or radiotherapy + hyperthermia + chemotherapy from October 1997 to September 2003. The first 100 hyperthermia treatments fulfilling the only selection criterion: no displacement of the thermometry catheter along the insertion length during the treatment, were included in the study, resulting in 43 patients with one-to-five treatments/patient (median 2). Using RHyThM (Rotterdam Hyperthermia Thermal Modulator), for each single treatment tissue type, was defined on the basis of information given by a CT scan in radiotherapy position. A step change in the slope of the profile of the first temperature map was identified to verify the insertion length of the catheter. Results: The average T50 (median temperature) in bladder tumour indicative, vagina tumour contact and rectum tumour indicative was 40.9 ± 0.9°C, 39.7 ± 0.9°C and 40.6 ± 0.8°C, respectively. The average normal tissue T50 in bladder, vagina and rectum was 40.8 ± 0.9°C, 40.1 ± 0.9°C and 40.7 ± 0.8°C, respectively. The differences between bladder tumour indicative T50 and bladder normal tissue T50 and also between vagina tumour contact T50 and vagina normal tissue T50 were significant (p = 0.0001). No statistical difference was found between rectum tumour indicative T50 and rectum normal tissue T50. Conclusion: At present the cause of the temperature difference is not known. However, as the difference between tumour (indicative/contact) and normal tissue is very small and considering also the inaccuracy in the tissue type assignment it can be stated that this study does not provide sufficient evidence to conclude that the statistical difference has clinical relevance. Therefore, it was concluded that at this time there is no need to differentiate between normal and tumour tissue in intra-luminal thermometry.