Permalloy films (83 wt.% Ni‐17 wt.% Fe) epitaxially grown on NaCl, were annealed by electron bombardment in an electron microscope. Perfect single‐crystal diffraction patterns indicated the presence of the [100] parent crystal and [122] twin crystals. Fringe patterns observed on electron micrographs were identified by dark field microscopy and electron diffraction as being caused by platelets of twins, 100–400 A thick, lying parallel to {111} planes of the parent crystal. The nonintegral reflections, commonly observed in conjunction with twin reflections, were shown to be caused by double diffraction.