Spherical MgCl2-supported Ziegler-Natta catalysts containing internal donors, such as diethyl phthalate, diisobutyl phthalate, and di-n-octyl phthalate, have been prepared. The effects of external donors, phenyltrimethoxysilane, phenyltriethoxysilane, and diphenyldimethoxylsilane, on the propylene polymerization catalyzed by these catalysts were studied. The results indicate that the external donors not only led to an increase in the isotactic index, but also affected the morphology of resultant polymer particles. (C) 2004 Wiley Periodicals, Inc.