Selected area electron diffraction pattern (SADP) and transmission electron microscopy (TEM) measurements were carried out to investigate the spontaneously ordered structure in CdxZn1-xTe epilayers grown on GaAs (100) substrates. The SADP showed superstructure reflections with symmetrical intensity, and the high-resolution TEM (HRTEM) micrographs showed doublet periodicity in the contrast of the {100} lattice planes. The results of the SADP and the HRTEM measurements showed a Cu3Au-type ordered structure was formed in the Cd(x)Z(1-x)Te epilayer. The present results can help improve understanding of the Cu3Au-type ordered structures in CdxZn1-xTe epilayers grown on GaAs substrates. (c) 2005 Elsevier Ltd. All rights reserved.