Dislocation boundaries in drawn single-crystal copper wires produced by Ohno continuous casting have been studied via electron backscattering diffraction and transmission electron microscopy. In the undeformed wires, there are subgrains with misorientation angle lower than 4.2A degrees. For the cold-drawn wires, we measured misorientation angle and spatial distribution of dislocation boundaries, analysing the formation mechanism of dislocation boundaries parallel to drawing direction. Regarding spatial distribution of high-angle dislocation boundaries, at the strains more than 2.77, the boundaries spread from the centre to the surface regions with increasing strain. Regarding the angular distribution of dislocation boundary misorientation, at the strain lower than 2.77, there is one peak lower than 5A degrees. Increasing the strain to 4.12, a bimodal distribution of misorientation angles is observed. One is lower than 5A degrees, and the other is between 45 and 50A degrees. For dislocation boundaries parallel to drawing direction, although at low strains there are different deformation bands with different microstructures, at high strain the microstructures are characterized as dislocation boundaries parallel to drawing direction formed by two approaches: the interaction between two kinds of boundaries and the increase in misorientation angle of boundaries shared by some dislocation cells.