It is shown that relatively thick (10 000‐Å) films of aluminum thinned by sputter‐etching exhibit an increase in both the room‐temperature and helium‐temperature resistivities, and that this increase is too large to be explained in terms of the Fuchs (thickness) size effect or by changes in the specular scattering probabilityp. A part of the increase in the helium‐temperature resistivity anneals out after 2 h at 250°C but a large increment remains. It is suggested that topographic and structural changes in the films may be responsible.