The residual electron density distribution in alpha-Al2O3 has been studied with single-crystal X-ray diffraction intensity data. In addition to conventional least-squares anharmonic refinement up to the fourth-rank tensors (R=0.0081), a method for obtaining experimental atomic scattering factors by utilizing occupation parameter refinement was tested. It has been found that this method is convergent once the basic crystal structure is well established (R=0.0066). Although there were no prominent electron density residuals, several weak (approximately 0.1e angstrom-3 in height) residuals including some resembling those due to bonding electrons were detected.