Magnetostriction constants of MnxFe3−xO4at room temperature are reported and related to the cation distribution in these spinels. Octahedral Fe2+ions give a positive contribution to &lgr;111. The contribution to &lgr;100of octahedral Mn3+ions is negative in this system and is not a linear function of the Mn3+concentration, which may be caused by local stresses in the crystal.