By considering variations in topology, material properties and adhesion characteristics, the micromechanical stress states devel- oped within ®brous composites that contain a heterogeneous interphase region has been predicted numerically. The formulation of a generalized computational simulation developed to treat speci®c features of these materials yields stress predictions using a ®nite- element approximation. The parametric description of the geometry and the incorporation of material inhomogeneities by a sequence of homogeneous subregions allows for the treatment of any material combination including closely packed composites and conditions of imperfect adhesion. Considering square and hexagonal arrays of ®bers, two major ®nite-element grids were generated where the features and the constrains are automatically being assigned. Numerical results illustrate the in¯uence of material parameters on local critical stress states and indicate regions of high stress concentration. It has been proved that, ®ber interaction substantially intensi®es stress concentrations within the interphase region, although imperfect adhesion relieves stresses