Antiphase boundaries are observed in epilayers of GaAs grown by organometallic vapor phase epitaxy on Ge substrates and are then invariably found to show a tendency to facet. Stacking-fault-like fringes caused by the translation of adjacent grains give the information on the relative displacement of the two grains at these interfaces and show that this translation does not have a fixed magnitude for a particular interface but varies with the orientation of the interface. Preferred orientations of the antiphase boundaries and the rigid-body translations have been studied using transmission electron microscopy. Interactions between antiphase boundaries and interfaces have been examined here in heterolayer structures consisting of alternating layers of GaAs and AlxGal−xAs grown on an (001) Ge substrate. The possibility of using atomic-resolution imaging to investigate the atomic structure of APBs is illustrated and the images are compared with those predicted by image simulation.