The overall objective of this project was to investigate the use of local hyperthermia as a means for improving the potential utility of radiolabeled monoclonal antibodies for tumor therapy. Hyperthermia not only can alter tumor hemodynamics but also can affect antigen expression, catabolism and cytotoxicity. These studies were performed with the human/mouse chimeric anti-tenascin 81C6 antibody in an athymic mouse xenograft model. Variables that were found to be important included the duration and temperature of heating, as well as the timing of the hyperthermia relative to the time of labeled antibody administration.