Monodisperse porous alpha-Al2O3 nanoparticles with variable sizes were prepared by the homogeneous precipitation method and subsequent heat-treatments. The crystalline phases, morphologies and pore size distributions of the samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and N-2 adsorption/desorption. The diameters of porous alpha-Al2O3 nanoparticles obtained with an Al3+ concentration of 10 mmol/L were in the range of 200-500 nm, and the diameters of porous alpha-Al2O3 nanoparticles obtained with an Al3+ concentration of 0.5 mmol/L were in the range of 40-70 nm. The pore sizes of porous alpha-Al2O3 nanoparticles were approximately 6-14 nm. The porosity developed during the heating process due to phase transformation and shrinkage of precursor particles. The monodisperse porous alpha-Al2O3 nanoparticles have great potential to be applied in gas separation, catalyst supports and filters in a high temperature environment. (C) 2012 Elsevier B.V. All rights reserved.