A simple theological constitutive equation for immiscible blend is suggested in this work. The model is based on the ellipsoidal description of droplets. Droplet deformation is described by the ellipsoidal model, and droplet breakup/coalescence is considered to affect the droplet size only. The discrete breakup/coalescence process is approximated by a continuous dynamic equation. A simple resealing method is suggested to integrate the volume-preserving ellipsoidal deformation model and the droplet size evolution dynamics. The predictions of the model are compared with experiments in start up of shear and shear rate sweep modes. The agreement is quite satisfactory on transient and steady rheological properties, as well as the morphology of droplets. (c) 2007 The Society of Rheology.