Abstract The theory of high-energy electron diffraction into higher-order Laue zones (HOLZs) is extended to deal with absorption of, as well as coupling between, different states of the zeroth-order zone. The cross-terms generated give rise to diffracted intensities which are sensitive to the polarity of a HOLZ reflection. Limiting cases of the theory are taken to explain the various forms of HOLZ asymmetry observed at 〈001〉 axes of the common III–V and II–VI semiconductors. The asymmetries are found to be a remarkably stable measure of polarity for these materials.