Induction heating can be utilized to cause necrosis of neoplasm as a result of hyperthermia by a process involving the injection of particles having hysteresis heating characteristics into tissue either within or in close proximity to the neoplasm and then subjecting these particles to an alternating magnetic field sufficient to cause hysteresis heating. The frequency of the field is preferably sufficiently low so as to minimize eddy current and dielectric heating. The particles used are preferably initially located within a biologically inert liquid carrier which will facilitate the insertion of the particles within the body and which will automatically become non-liquid within the body so as to hold the particles in place. The actual heating is preferably carried out by positioning either the entire patient or the affected portion of the patient's body through a series of axially aligned, parallel, liquid cooled coils. Only one of these coils is connected to a power supply.