New experimental results describing the breakup of drops suddenly subjected to shearing forces sufficient to cause drop breakup are presented The experiments examine fluids which are immiscible and Newtonian under the conditions studied: These results and of her breakup mechanism results are then discussed in the context of combining them with kinematic information on more complex flows in order to predict drop size distributions in processing flows. By analyzing the time scales of various breakage mechanisms studied in simple shear flow and comparing them to the appropriate time scales in more complex flows, the relevant importance of a given mechanism in determining the daughter drop size distribution is predicted This type of time scale analysis is performed for flow in a cavity and flow in an extruder.