The temperature dependence of elastic‐diffracted intensities for polycrystalline Al films has been investigated at 296° and 77°K as a function of crystal thickness in the range 600–2500 Å. A quantitative agreement is found with the predictions of the BJR two‐beam approximation of the dynamical theory. This agreement, however, appears to be best for Al in a range of thickness below the anomalous absorption distance or where kinematical theory should apply.