Replica electron microscopy of rupture surfaces has been used to study the rupture process in solid `two-phase' systems obtained by dispersing colloidal carbon in rubber. Two parameters are introduced to characterize the surfaces; the total proportion of filler in the surface, and the proportion extracted by the gelatine first-stage replica. The latter quantity provides a measure of carbon-to-rubber adhesion in the rupture surface, whilst values obtained for the former quantity indicate that the rupture deviates strongly from a random plane through the material.The results, together with a correlation found between adhesion and tearing energy, may be largely explained in terms of the local concentrations of stress which occur at the particles of the dispersed phase.