Stoichiometric cadmium-substituted magnetites CdxFe3-xO4 (x = 0, 0.25, 0,50, 0.75 and 1) were prepared by a standard ceramic method. It has been found that, after grinding, these Cd-ferrites can be oxidized under prolonged isothermal conditions at low temperature (<300 degrees C) whilst retaining the single spinel phase. The oxidation and the resulting nonstoichiometric solid solutions between CdFe2O4 and gamma-Fe2O3 have been investigated by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis and infrared spectroscopy. A cation distribution for defect solid solutions of maghemite, gamma-Fe2O3, and cadmium ferrite has been proposed.