The kinetics of peroxide-induced degradation of Polypropylene have been determined by comparing full molecular weight distributions from size exclusion measurements (SEC) to rigorously modeled ones. The basic idea is the unique effect of each mechanism on the shift in MWD. The existence of termination by disproportionation and transfer to polymer could thus be assessed, turning out to be highly coupled. The impact of residence time distribution and imperfect mixing on the MWD shift has been examined. The application of a straightforward mixing model suggests such effects to be non-important.