The aim of this work was a transmission electron microscopy (TEM) study of the microstructure of a tungsten heavy alloy (WHA). Due to the profound differences in hardness of the tungsten particles and the Ni-Fe-W matrix a special TEM specimen preparation method had to be employed. Despite the presence of some artifacts the investigations gave the microstructure details of as-sintered and annealed cold-rolled specimens. It was found that the WHA annealed after cold rolling reveals a refinement of the microstructure of some tungsten particles and of the matrix in the areas close to the particles. (C) 2003 Elsevier Science B.V All rights reserved.