Crystallization behaviors, spherulite growth and structure, and the crystallization kinetics of polypropylene (PP)/ethylene-alpha-olefin copolymer (mPE)/high-density polyethylene (HDPE) ternary blends and of mPE/HDPE binary blends have been studied using polarizing optical micrography (POM) and differential scanning calorimetry (DSC). In mPE/HDPE blends, large pendant groups of mPE disturbed spherulite growth of HDPE, leading to a different crystallite morphology and isothermal kinetics. Non-isothermal proper-ties, morphology, and isothermal crystallization kinetics of PP in ternary blends were significantly influenced by the composition and crystallization behavior of the mPE/HDPE binary blends as well as the crystallization condition. (C) 2004 Society of Plastics Engineers.