The weight ratio of PE and PS in ternary PS/SBR/PE blends has been changed at constant SBR content (25 wt%)When the matrix is either PE or PS, the dispersed phase has a core-shell structure with SBR forming the shell. The size of the core expectedly increases with the content of the core-forming polymer. In some composition range, the three phases are simultaneously continuous, SBR being localized in between the co-continuous PE and PS phases. The ultimate mechanical properties of the ternary blends containing SBR/PE and SBR/PS core-shell dispersed phases are close to the properties of the PS/SBR and PE/SBR binary blends, respectively. Some synergism in the elongation at break of the ternary blends is observed when core-shell SBR/PS phases are dispersed in PE matrix. (C) 2000 Elsevier Science Ltd. All rights reserved.