The effect of stacking fault energy (SFE) on the evolution of microstructures during wire drawing at room temperature has been studied in pure aluminium, pure copper and Cu-2.2% Al and Cu-4.5% Al alloys which covers a range of SFE values from 4 to 166 mJ m(-2). The compositions are expressed in atomic parts per million by weight. The microstructures have been characterized from samples obtained by deforming rods of these materials to true wire drawing strain values of up to 1.47. A decrease in the SFE value changes the deformation mechanisms from the formation of cell structure and their size refinement in a high SFE material to the formation of deformation bands and deformation twins in a low SFE materials. The Cu-2.2% Al alloy deforms by deformation bands at low true strain values while deformation twins within the bands control the deformation mechanisms at higher true strain values. The alloy, Cu-4.5% Al, with the lowest SFE value deforms only by deformation twins even at low true strain values and the presence of overlapping and intersecting deformation twins are the dominating features as the rods are drawn to higher true wire drawing strains.