A comparison of kinematic and dynamic approaches of x‐ray diffraction is made for multiple InGaAs/InGaAlAs quantum wells (MQW), around 002 and 004 reflections, as a function of strain and thickness. A domain of validity of the kinematic approximation is then defined. It turns out that the kinematic approximation is sufficient in the case of typical structures for MQW lasers or modulators. An automatic procedure including kinematic treatment of double‐diffractionXand photoluminescence data is proposed, which allows us to determine precisely the compositions, thicknesses, and even the band offsets of MQW structures. This procedure is applied to a 20 period sample. The results are confirmed by transmission electron microscopy measurement. ©1996 American Institute of Physics.