The rheology and morphology evolution of nondilute and concentrated immiscible blends were investigated in this paper. A theoretical model was established by a Hamiltonian formalism. The interactions between droplets were integrated in the morphology-dependent drag coefficient. The phenomenological parameters in the model were determined by the comparisons with the dilute emulsion model and the Krieger-Dougherty model. The model showed better predictions in the shear viscosity and first normal stress difference than that of the dilute emulsion model. The effects of volume fraction on droplet deformation were also predicted and compared with the numerical simulations. (c) 2005 Wiley Periodicals, Inc.