The formation and evolution of MnFe2O4 ferrite phase coprecipitated with NaOH from MnO2 and FeSO4 . 7H(2)O in aqueous solution are discussed, grounded on X-ray diffraction and derivatographic data, IR spectra and magnetic measurements. The results concerning the nature of the initial coprecipitates, their structural changes during ageing in the original solutions at temperatures in the range 25-95 degrees C as well as the structure of the resulting ferritic phases are presented.