The effect of magnetic annealing on the ferromagnetic resonance linewidth of a single crystal of normal ferrites or of ferrous ferrite containing a small concentration of substitutional Co2+ ions is calculated. The calculations are based on a mechanism of magnon scattering induced by the ion-to-ion variation of the spin-orbit interaction as suggested by Haas and Callen. The result obtained shows that besides the isotropic part of linewidth, there is an anisotropic part, which depends on the direction of the field applied during annealing as well as on the direction of magneti2ation. For each percent of cobalt the maximum directional variation of linewidth may be of the order of 4 oersted.