A background function including the correlation between the thermal displacements of atoms in Rietveld refinements has been proposed. For the purpose to investigate the availability of the background function, neutron scattering measurements from powder sample of AgBr at 290 and 7 K were performed. Rietveld refinements of the scattering data by the newly proposed and the formerly used background functions have been carried out, The new background function gives somewhat lower R factors at 290 K than the previous one does. (C) 2000 Elsevier Science B.V. All rights reserved.