It is known that significant heating can be generated by magnetic hysteresiseffects in small ferromagnetic particles exposed to a rapidly alternatingmagnetic field. If such particles can be made to infiltrate the vascular bedsurrounding a tumour by intravascular infusion then it may be possible togenerate sufficient heating to destroy the tumour by hyperthermia. One of theconstraints on such a technique is the limited amount of magnetic materialthat can be delivered to a tumour via the intravascular route and theconsequent heating that can be induced by this material. Here, we report on aseries of experiments in which doses of microspheres containing differentamounts of ferromagnetic material were infused into rabbit kidneys via therenal artery with the aim of testing whether adequate tissue heating could beachieved using realistic concentrations of the embolised material. Heatingrates were measured for each infused quantity under similar conditions withthe animal alive and dead to examine the role of blood flow in the heatingprocess. The results show that tissue temperatures above the therapeuticthreshold of 42 °C can be readily achieved using this method withclinically relevant concentrations of microspheres in living tissue.