Rheological responses in capillary flow extrusion for syndiotactic polypropylene (sPP) are studied along with the linear viscoelastic properties. It is found that sPP produced by a metallocene catalyst shows a high level of the onset shear stress for flow instability as compared with conventional isotactic polypropylene. This should enable operation of extrusion processing at high output rates. (C) 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:185-191, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20159