Experiments to test the effect of directional stress on the remanent magnetization of magnetite bearing rocks and nickel polycrystallites are described. The TRM of volcanic rocks under repeated compression of less than 1kb was found to reveal a nearly reversible change in intensity. The intensity increases when the direction of compression is perpendicular to that of TRM and decreases when the compression is parallel, in accordance with the theory of magnetoelasticity. Stability of IRM and PRM induced in previously workhardened nickel rods under compression is compared with that of TRM. TRM of a nickel polycrystallite under compression changes in a manner similar to that of volcanic rocks. However, no reversible change was found for IRM, even the compressional stress did not exceed a few hundred bars. The results, combined with the magnetic susceptibility of rocks under compression, can be used for estimation of seismo-magnetic effects.