The purpose of this study was to produce aspirin-impregnated microspheres of chitosan/poly( acrylic acid) copolymer in order to evaluate the release characteristics as a function of pH, simulating the fluids in the gastrointestinal tract. Chitosan microspheres were obtained by the coacervation-phase separation method, induced by the addition of a non-solvent (NaOH 2.0 M solution). The microspheres were cross-linked with glutaraldehyde, reduced with sodium cianoborohydride and grafted with poly(acrylic acid). The impregnation of aspirin into chitosan/poly(acrylic acid) copolymer microspheres was achieved by the dissolution of the drug in water: ethanol (2:1), which was adsorbed by the microspheres for 24 h at 25 degreesC. The efficiency of aspirin impregnation was high (similar to 94%). The approach employed herein in the production of aspirin-impregnated microspheres using chitosan/poly(acrylic acid) can be a suitable drug-release control system.