A diffraction analysis in the transmission electron microscope was carried out onInxGa1−xNlayers grown on (0001) sapphire by metalorganic vapor phase epitaxy on top of thick GaN buffer layers. It is found that the ternaryInxGa1−xNlayers can be chemically ordered. The In and Ga atoms occupy, respectively, the two simple hexagonal sublattice sites related by the glide mirrors and helicoidal axes of theP63mc symmetry group of the wurtzite GaN. The symmetry of the ordered ternary is subsequently lowered by the disappearance of these operations, and it is shown to agree with the P3ml space group. ©1998 American Institute of Physics.