For the first time controlled nucleation and crystallization were studied for 40Fe(2)O(3)-20CaO-40SiO(2) (wt %) glass which is useful as thermoseeds for hyperthermia of cancer. To investigate the crystallization mechanism of Fe2O3-CaO-SiO2 glass, the Avrami parameter and the activation energy for crystallization were measured by isothermal and non-isothermal processes using classical and differential thermal analysis techniques. Magnetite was the main crystal phase and the maximum nucleation and crystal growth temperatures were 700 and 1000 degrees C, respectively. The value of kinetic parameters such as the Avrami constant, the activation energy, and the frequency factor, determined using isothermal and non-isothermal processes showed excellent agreement. The slopes of the Kissinger, and Matusita and Sakka plots were almost parallel to each other, and, consequently, crystal growth is believed to occur on a fixed number of nuclei, the m values being considered to be the same as the n values. Using m = 1.5 and n = 1.5, it was found that diffusion-controlled crystal growth with a constant number of nuclei occurred and these result are in excellent agreement with those determined by the classical technique.