The transition from the tetragonal (I4/mcm) to the orthorhombic (Imma) structure associated with a change in A- to CE-type antiferromagnetism in the Pr0.5-xNdxSr0.5MnO3 has been investigated by X-ray diffraction as well as magnetization and resistivity measurements. The transition is found to occur between x = 0.1 and 0.2. (C) 2002 Elsevier Science Ltd. All rights reserved.