Epoxy-aided dispersion of nanoclay particles in a glassy polymer, polymethylmethacrylate (PMMA), was studied using melt-blending technique. Organically treated nanoclay particles were dispersed in PMMA using mixtures of aromatic and aliphatic epoxies to yield three-phase composite materials, the mechanical properties of which were evaluated and compared with PNMA-nanoclay, epoxy-nanoclay, and PMMA-epoxy composite systems as function of nano- and micro-dispersed domains of phase separated epoxy and nanoparticles. Wide-angle-X-ray diffraction patterns and transmission electron microscope images revealed that the clay particles were in fully exfoliated state in the three-phase composites provided the ratio of epoxy to clay was 10. However, the dispersion of nanoclay to the scale of individual platelets was not achieved as exfoliated clay particles remained as aggregates inside phase separated epoxy domains of approximately I Km in diameter. Nevertheless, the values of tensile and impact strengths showed significant improvement over PMMA and PMMA-clay composites. (C) 2003 Elsevier Science Ltd. All rights reserved.