AbstractThe structure of polypropylene fibers formed by different spinning conditions was studied. The investigations were carried out using wide‐angle X‐ray scattering (WAXS) and small‐angle X‐ray scattering (SAXS) methods. It was stated that in noncolored fibers the mesophase and the monoclinic α forms were formed. The highest content of the mesophase was observed for fibers extruded at the higher temperature and taken at the medium take‐up velocity. In fibers colored with quinacridone pigment the structure containing the monoclinic α and the trigonal β forms was obtained. The highest content of the β form occurred in fibers taken at the lowest take‐up velocity. The increase of the take‐up velocity caused a rapid drop in β form content. In fibers taken at higher velocities only the α form was formed. It was found that the content of different forms as well lamellar thickness depends on crystallization conditions, which were influenced by the formation parameters. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3364–3370, 2003