The isotatic polypropylene (i-PP) plastically deformed by uniaxial plane strain compression was investigated using X-ray diffraction and transmission electron microscopy. The apparent crystallinity was evaluated by means of X-ray diffraction with a profile matching using a FULLPROF code. Two crystalline phases, alpha and beta, were identified in the non-deformed polymer as well as with an amorphous halo. The deformation with 3, 10 and 100 MPa, induces an increase of the amorphous halo. The microstructural orientation of the i-PP, before and after deformation was evaluated using the "Quantikov" image analysis of transmission electron microscopy (TEM) data. The non-deformed material presents spherulitic structure, without any preferential orientation. The high resolution, in the nanometer scale, shows two preferential orientation axes. The deformation at 3, 10 and 100 MPa, affects the spherulitic, as well as, the lamellae structure, introducing fiber orientation, a break up of the lamellae in to small blocks and consequently amorphization of the system. (C) 2004 Elsevier Ltd. All rights reserved.411129138