Attempts were made to study rheology and morphology of high impact polystyrene/ polyethylene (HIPS/PE) blends. The Effect of compatibilization using styrene-butadiene-styrene copolymer (SBS) and styrene-ethylene-butylene-styrene copolymer (SEBS) on their properties was also studied. The results of linear viscoelastic properties showed negative deviation of viscosity and elasticity from the mixing rules in low HIPS content blends, while positive deviation was observed for high HIPS content blends. The former was related to weak interface and the latter was attributed to the hydrodynamic interaction of PE and PB particles. A wide range of co-continuity was observed for HIPS/PE blends which decreased using compatibilization. It was found that SEBS had better efficiency of compatibilization than SBS due to lower molecular weight and the presence of ethylene block in SEBS structure. The fracture behavior of low and high HIPS content blends showed different mechanism because of higher volume contraction of PE than HIPS in solidification process and also different mechanical properties of HIPS and PE. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2235-2245, 2009