Iron oxide powders were obtained by the isothermal decomposition of ferric citrate in an oxygen atmosphere at different temperatures. Throughout the experiments, the product of decomposition was a mixture of maghemite (γ-Fe 2 O 3 ) and hematite (α-Fe 2 O 3 ) with different relative proportions and particle size distributions. After TGA and DTA measurements, a decomposition temperature of 300 o C was chosen, and a maximum specific saturation magnetization of about 40 emu/g was obtained. Most of the product particles were less than 1 μm in size, including a superparamagnetic fraction, as evidenced by Mossbauer spectroscopy.