[en] A study was made of electron-beam-induced crystallization of sections of a detached barrier-type anodic film formed on aluminium in ammonium pentaborate solution. On exposure to the electron beam, telling changes are evident in the section, proceeding more rapidly in a region of the film originally adjacent to the metal-film interface but eventually spreading throughout the film section. The results suggest that the virtually pure alumina region, separated from the electrolyte by the borate-containing region, crystallizes initially and hence this technique becomes a rapid method for direct assessment of apparent transport numbers. (Auth.)