The effect of Co addition on microstructures of Nd-Fe-B/Ta multilayered films was investigated by scanning transmission electron microscopy. It was found that fine Nd2Fe14B grains with a mean diameter of less than 100 nm grew to columnar structures and their c-axes were preferentially oriented perpendicular to the film plane, and that these states were more pronounced in the Co-doped film. It was also found that pure Nd and Nd-rich phases precipitated and distributed in the Nd2Fe14B layer, and that more pure Nd phases precipitated in the Co-doped film. Moreover, discontinuity of the Ta layer and the occurrence of voids were observed and it was presumed that the crystallization of Nd2Fe14B started with a slight delay after the deposition of the film had been completed. (c) 2005 Elsevier B.V. All rights reserved.