The ultrasonic degradation of polystyrene and poly(vinyl acetate) in chlorobenzene was studied. The time evolution of the molecular weight distributions (MWDs) were determined by gel permeation chromatography of the degraded samples. The data were analyzed with a continuous distribution kinetics model that treats the molecular weight as a continuous variable. Since the chain cleavage in the ultrasonic degradation of polymers occurs preferentially near the midpoint of the polymer backbone, a stoichiometric kernel that describes scission at the middle of the chain was used. The degradation rate coefficients of the polymers were determined using our model and was found to be 0.032 min-1. The model successfully simulated the number average molecular weight, the polydispersity of the degraded polymer and the time evolution of the molecular weight distributions.