ABSTRACT. Thermotherapy has been proven to be effective for the treatment of various tumors, including glioma. We determined whether tumor necrosis factor-alpha (TNF-α) is involved in the regulation of the biological processes of glioma development. Reverse transcriptionpolymerase chain reaction (RT-PCR) and immunocytochemistry were used to investigate the levels of TNF-α mRNA and heat shock factor-1 (HSF1) protein, respectively, in glioma cells. Radioimmunoassay was used to dynamically monitor the contents of TNF-α in the nutrient fluid of C6 cells after thermotherapy treatment. Crystal violet staining was used to determine glioma invasiveness. The most obvious increases in HSF1 protein and TNF-α mRNA in C6 cells were observed at 30 and 60 min after thermotherapy, respectively. In addition, the radioactivity of TNF-α in the culture fluid of the C6 cells reached a peak after 120 min of thermotherapy. In addition, glioma invasiveness decreased and the concentration of TNF-α reached a maximum after 120 min of thermotherapy. Our results show that the decrease in thermotherapy-mediated glioma invasiveness is due to the accelerated release of TNF-α, which could promote the release of HSF1 from neurospongioma cells.