The pH-sensitive hollow poly(N,N'-methylene bisacrylamide-co-methacrylic acid) (P(MBAAm-co-MAA)) microspheres were prepared by a two-stage distillation precipitation polymerization to afford a coreshell poly(methacrylic acid)/poly(N,N'-methylene bisacrylamide-co-methacrylic acid) (PMAA/ (P(MBAAm-co-MAA))) microsphere with subsequent removal of poly(methacrylic acid) (PMAA) core. PMAA/P(MBAAm-co-MAA) core-shell microspheres were synthesized by the second-stage copolymerization of N,N'-methylene bisacrylamide (MBAAm) as crosslinker and the functional methacrylic acid (MAA) comonomer in acetonitrile with 2,2'-azobisisobutyronitrile (AIBN) as initiator. The pH-responsive properties of hollow P(MBAAm-co-MAA) microspheres were investigated by dynamic laser scattering (DLS). The loading and controlled-release behavior of the drug for hollow P(MBAAm-co-MAA) microspheres was strongly dependent on the pH values with doxorubicin hydrochloride (DXR) as a model molecule. The core-shell and hollow polymer microspheres were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectra (FT-IR), DLS and elemental analysis. (C) 2009 Elsevier Ltd. All rights reserved.