Hyperthermia is a new treatment modality to increase the tumoricidal effect of radiotherapy for choroidal melanoma. We have produced a ferromagnetic glass-ceramic composed of magnetite and wollastonite as a thermoseed for interstitial hyperthermia. The stable oxidized ceramic produced sufficient heat by hysteresis loss upon exposure to an alternating magnetic field. We studied its heat-generating properties and evaluated its possible application to ocular hyperthermia. Agar model and rabbit eye studies showed that the heat generated by the ceramic was less affected by its orientation in the magnetic field than metal alloy thermoseeds and that the retinal surface was heated to 43.5 degrees C in less than 7 min without heating the surrounding tissue. Additionally, this heating system showed a good temperature stability of +/- 0.1 degrees C under steady-state conditions without using a controller. The new glass-ceramic shows promise as a thermoseed in ocular hyperthermia.