Résumé : The aim of this paper is to show that different assumptions for the interaction cross sections of low-energy electrons in polycrystalline aluminum targets lead to very different calculated values of secondary-electron yields, either in backscattering or in transmission. We emphasize the importance of the description of elastic collisions, of the choice of the dielectric function, and the role of ionizing collisions. We indicate that the comparisons between the published theoretical results are somewhat intricate due to the differences in the transport description and in the choice of cross sections. © 1993 The American Physical Society.