We develop a set of evolution equations describing the effects of a general deformation field on the shape, size, and orientation of constant-volume droplets suspended in a Newtonian fluid. The rheological characteristic functions of this incompressible and immiscible polymer blend model are also derived in tandem with the above-mentioned set. The constant-volume constraint is implemented using a recent methodology (Edwards BJ, Dressler M, Grmela M, Ait-Kadi A (2002) Rheological models with microstructural constraints. Rheo Acta (in press)) and discussed relative to the similarly volume-constrained model of Almusallam et al. (Almusallam AS, Larson RG, Solomon MJ (2000). A constitutive model for the prediction of ellipsoidal droplet shapes and stresses in immiscible blends. J Rheol 44:1055-1083). Sample results are reported for step-strain and shear relaxation profiles.