The effect of phase interaction induced by reactive compatibilization during high shear and extensional flow in polyamide (PA6) and ethylene-co-butyl acrylate (EBA) blends was studied using advanced dual bore capillary rheometer. The viscosity-composition behavior of the uncompatibilized PA6/EBA blends exhibited negative deviation behavior from log-additivity rule. The interfacial slip mechanism, operative between the matrix PA6 and dispersed EBA during shear flow was studied by the use of Lin's and Bousmina-Palierne-Utracki (BPU) model for viscosity for the blends under the processing conditions. On the other hand, the compatibilized PA6/EBA-g-MAH(0.49)/EBA blends with varying dispersed phase volume fraction show positive deviation behavior. The reactive compatibilizers EBA-g-MAH(0.49) and EBA-g-MAH(0.96) increased the phase interaction with adequate reduction in the dynamic interfacial tension, which favored the particle break-up and stabilized the morphology in the compatibilized blends. The extensional viscosity of the blends has enhanced because of the inclusion of EBA in all the uncompatibilized and compatibilized blends. The melt elasticity and elasticity function were systematically studied from first normal stress coefficient functions (psi(1)). The variation in the recoverable shear strain (gamma(R)), shear rate dependent relaxation time (lambda) and shear compliance (J(c)) under various shear rates were thoroughly analyzed for all the blend compositions. POLYM. ENG. SCI., 48:2482-2498, 2008. (C) 2008 Society of Plastics Engineers