The geometrical, energetic and electronic properties of the low-pressure trigonal phase of B2O3 are studied theoretically at density functional theory level. Different methods and types of basis sets are used and the corresponding results are compared for two previously proposed structures with space group symmetries P3(I)21 and P3(I). Based on the comparison of calculated and experimental structure parameters, and the calculated lattice energies of the two structures, it is concluded that the ground-state structure of B,03 has P3(I)21 symmetry. This is in agreement with a recent analysis of the spectroscopic data. (c) 2005 Elsevier B.V. All rights reserved.