The main purpose of the present work was to establish the effect of external magnetic field on the elastic modulus. We have prepared poly(dimethyl siloxane) networks loaded with randomly distributed carbonyl iron particles. It was found, that the elastic modulus of magnetoelasts could be increased by uniform magnetic field. In order to enhance the magnetic reinforcement effect, we have prepared anisotropic samples under uniform magnetic field. This procedure results in formation of chain-like structures from the carbonyl iron particles aligned parallel to the field direction. The effect of particle concentration, the intensity of uniform magnetic field as well as the spatial distribution of particles on the magnetic field induced excess modulus were studied. It was established that the uniaxial field structured composites exhibit larger excess modulus compared to the random particle dispersions. The most significant effect was found if the applied field is parallel to the particle alignment and to the mechanical stress. A phenomenological approach was proposed to describe the dependence of elastic modulus on the magnetic induction. The magnetic field sensitive soft materials with tuneable elastic properties may find usage in elastomer bearings and vibration absorber. (c) 2005 Elsevier Ltd. All rights reserved.