The mechanisms of microstructural evolution in copper have been investigated by ECAP, TEM and EBSD in order to characterize the microstructure after successive passes. The effect of initial grain size, die angle and pass sequences on the forination of ultrafine grain structure have been analysed. Texture evolution is discussed based on EBSD results. These experimental results are interpreted in terms of a preliminary model with four successive stages: homogeneous dislocation distribution; elongated sub-cell formation; elongated sub-grain formation; break-up of sub-grains into equiaxed units; sharpening of grain boundaries and final equiaxed ultra fine structure.