Repetitive Upsetting Extrusion (RUE) is a relatively new severe plastic deformation (SPD) process in which two conventional metal forming operations such as upsetting and extrusion has been combined to impart large plastic strain. Though originally invented to process powder materials for bulk mechanical alloying, a more recent study on the process has revealed that by suitably modifying the die design, the process can be used to impart large deformations in bulk materials as well. Using this new die, oxygen free high conductivity (OFHC) copper has been subjected up to 10 cycles of RUE. Microstructures across the cross-section of the RUE processed samples were evaluated using optical, scanning and transmission electron microscope to ascertain the deformation behaviour and the mechanism of grain refinement. The results obtained are presented and discussed. © (2012) Trans Tech Publications.