Some polyolefin elastomers were compared as compatibilizers for blends of polypropylene (PP) with 30 wt %. high-density polyethylene (HDPE). The compatibilizers included a multiblock ethylene-octene copolymer (OBC), two statistical ethylene-octene copolymers (EO), two propylene-ethylene copolymers (P/E), and a styrenic block copolymer (SBC). Examination of the blend morphology by AFM showed that the compatibilizer was preferentially located at the interface between the PP matrix and the dispersed HDPE particles. The brittle-to-ductile (BD) transition was determined from the temperature dependence of the blend toughness, which was taken as the area under the stress-strain curve. All the compatibilized blends had lower BD temperature than PP. However, the blend compatibilized with OBC had the best combination of low BD temperature and high toughness. Examination of the deformed blends by scanning electron microscopy revealed that in the best blends, the compatibilizer provided sufficient interfacial adhesion so that the HDPE domains were able to yield and draw along with the PP matrix. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 1945-1952, 2009