The coexistence of a phase separation and an ordered structure in CdxZn1-xTe epilayers grown on GaAs(001) substrates by using molecular beam epitaxy was investigated. The results of selected-area electron diffraction pattern and transmission electron microscopy measurements showed that ordered structures, such as CuPt-type and CuAu-I-type ordered structures, together with a spinodal-like phase separation were formed in the CdxZn1-xTe/GaAs heteroepitaxial layers. The coexistence of the phase separation and the ordered structures is discussed. (C) 2006 American Institute of Physics.