The Fe?Mo sample mechanically alloyed for 250?h under air atmosphere was exposed to a series of isothermal and isochronal treatments with the aim to follow changes in the structure and magnetic properties regarding relaxations of strains and defects and stability of chemical composition. For this purpose x-ray diffraction, positron annihilation, scanning and transmission electron microscopy, and M?ssbauer spectrometry were applied and supplemented by magnetic measurements. The temperatures for the magnetic studies were selected from the thermomagnetic curve of the as-prepared sample. The time interval of isothermal treatments was chosen from 0?300?min.