In this work, the mutual effect of the filler aluminum hydroxide Al(OH)(3) and the compatibilizers ethylene-propylene copolymer (EPR) and ethylene-vinyl acetate copolymer (EVA) on the properties of blends based on polyethylene (PE) and polypropylene (PP) was studied. The microstructural and morphological changes as well as mechanical features of samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and by tensile tests. Morphology of the samples prepared with the compatibilizers, and filler is much finer in comparison to virgin blend. Due to established interaction between components that enhance the intimate adhesion among the components finer droplets dispersion within the blends matrix is observed. The addition of the filler and compatibilizers produced an increase in the elasticity particularly for the samples prepared in two-stage extrusion process where filler is first extruded with PE matrix and then extruded with other polymers of the blends. (C) Koninklijke Brill NV, Leiden, 2009