A high-density polyethylene with grafted maleic anhydride units has been investigated as a compatibilizer for high-density polyethylene with polyamide 6. The material acts as an effective compatibilizer, causing a marked reduction in dispersed phase size as well as an increase in tensile strength and toughness. Compatibilizer also affects the glass-transition temperature, crystallization kinetics, and amount of crystalline material for certain blend compositions. The addition of zinc cations, which are effective in increasing ethylene-acid copolymer compatibilizer performance in low-density polyethylene /polyamide blends, has little, if any, effect on compatibilizer performance in these high-density polyethylene /polyamide blends. (c) 2006 Wiley Periodicals, Inc.