Copper single crystals were subjected to equal-channel angular pressing (ECAP) via the so-called route A and Bc, in order to examine the influence of initial crystallographic orientation and processing route on microstructure development and grain fragmentation. Microstructural changes were examined by transmission electron microscopy (TEM). The pressing via the route Bc resulted in finer microstructure for all orientations in terms of grain size, equiaxiality and orientation scattering after four passes. Effect of initial crystallographic orientation on the grain refinement was also recognized, and it might be attributed to heterogeneous deformation such as shear bands, whose formation is strongly orientation dependent. After eight passes, however, the effect of processing route and initial orientation cannot be recognized.