Polymer blends provide an efficient way to produce new materials. It is known that the final morphology of polymer blends develops rapidly during the blending process. During the initial stages of polymer blending, lamellar structures or sheets are formed and this is an effective way to achieve quick reduction in size. Thus, the millimeter sized polymer pellets are deformed and broken up into sub-micron sized droplets rapidly. Studying the deformation and breakup of a polymer drop in a second polymer melt will help us to understand how one polymer disperses into another, and will give valuable insight into how the final drop distribution is obtained. Visualization studies on drop breakup in polymer systems suggest that the normal stress plays an important role for polymer-polymer systems, and contributes to phenomena such as widening of drops or elongation in the vorticity direction. A good understanding of the mechanism of drop deformation and breakup is crucial to control the dispersion in polymer blends. A specially designed twin-screw extruder and a special transparent Couette flow cell were used to study drop breakup at high temperature. During Couette experiments, the two cylinders counter-rotated to keep the drop in a stagnation position. In polymer systems, it was found that drop breakup occurs even when the viscosity ratio is greater than 3.5 (impossible for Newtonian systems). It may be inferred that the critical breakup condition for polymer systems is different from that for Newtonian systems since polymers are viscoelastic and shear-thinning. The drop size determines to a great extent, the type of drop breakup mechanism and the critical point when the mechanism changes. There is a big jump in the critical shear rate when the mechanism changes from breakup in the flow direction to breakup in the vorticity direction.