The rheological behaviors of noncompatibilized and compatibilized polypropylene/polyethylene terephthalate blends (80/20) in relation with their morphology were studied at two constant levels using maleic anhydride-modified styrene-ethylene-butylene-styrene polymer. By scanning electron microscopy of cryofractured surfaces, the morphology of the blends was examined after etching. The frequency sweep and step strain experiments were carried Out for the blends. The frequency sweep results indicated that increasing the compatibilizer causes behavioral changes of the rheological properties, which could be related to the aggregation of the dispersed particles with rubbery shell. Also, the frequency sweep and step strain experiments in linear region, after cessation of simple steady shear flow with various preshear rates (higher shear stress values than G(p)(1)), were done on compatibilized blend. The results showed that the morphology characteristics, defined by the aggregation of the dispersed particles based on rheological experimental data, were destroyed and replaced by an alignment in the flow direction for present imposed shear rates. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 441-448, 2010