The mechanism of formation of ellipsoidal hematite (alpha-Fe2O3) particles, obtained by homogeneous precipitation from ferric salt solutions under different experimental conditions, is reported, Monocrystalline ellipsoidal particles having an axial ratio of 6, precipitated by aging FeCl3 solutions in the presence of small amounts of phosphate anions, are formed by an ordered aggregation of smaller ellipsoids. The nature of the forces involved in this process and the role played by phosphate anions are discussed, Ellipsoidal hematite particles (axial ratio 1.65) obtained by aging Fe(NO3)(3) acidic (HNO3) solutions were found to contain a certain amount (approximate to 8%) of goethite (alpha-FeOOH) in the particle core. A formation mechanism involving the heterogeneous nucleation of hematite on initially precipitated goethite cores is suggested.