Dependence of strain distribution on Mg concentration in MgxZn1-xO layers on a-plane sapphire substrate grown by plasma-assisted molecular beam epitaxy was examined. Accurate determination of lattice parameters was performed using high resolution X-ray diffraction technique. Concentration of Mg was established by Rutherford backscattering spectrometry. These results show the non-linear relationship between the lattice parameters and Mg concentration. We observe the gradual gain of strain with the increase of Mg content in MgxZn1-xO layers, in particular in c-direction. Besides epitaxial layers on a-plane sapphire are biaxially strained similar to layers on c-plane sapphire. (C) 2017 Elsevier B.V. All rights reserved.