X‐ray diffraction has been used to study CdTe layers grown by molecular beam epitaxy on Cd0.96Zn0.04Te or InSb substrates with either (111) or (001) orientation. The layers are elastically strained up to a critical thickness, above which misfit dislocations are generated. Our experimental determinations of the critical thickness and the relaxation of the stress while increasing the layer thickness are different from predictions of the existing models. We present a discussion of relaxation based on the determination of the minimum energy state of the layer for a given thickness. We show that above the critical thickness, the layer relaxes so that the product of the stress by the thickness remains constant. This constant has been experimentally determined for both (111) and (001) orientation.