The crystal and magnetic structures of the charge ordered perovskite BiNiO(3) have been studied at temperatures from 5 to 300 K using neutron diffraction. Rietveld analysis of the data shows that the structure remains triclinic (space group P (1) over bar) throughout the whole temperature range. Bond-valence sum calculations based on the Bi-O and Ni 0 bond distances confirm that the charge distribution is Bi(0.5)(3+)Bi(0.5)(5+)Ni(2+)O(3) down to 5 K. The magnetic cell is identical to that of the triclinic superstructure and a G-type antiferromagnetic model gives a good fit to the magnetic intensities, with an ordered Ni(2+) moment of 1.76(3) mu(B) at 5 K. However, BiNiO(3) is ferrimagnetic due to the inexact cancellation of opposing, inequivalent moments in the low symmetry cell. (C) 2008 Elsevier Inc. All rights reserved.