Ultrasonic degradation studies of poly(methylmethacrylate; PMMA) and poly(butyl methacrylate; PBMA) m solutions are reported. Measurements of the molar mass distribution usmg gel permeation chromatography indicate very little evidence of degradation for shorter cham PMMA. For the higher molar mass PBMA. a progressive decrease in the number and weIght average molar mass was observed. The molar mass distribution progressively narrowed with mcrease m ultrasonic irradiation time. A decrease in viSCOSity of PBMA solution was also observed with increasmg irradiation time. The results show that there IS limiting molar mass below which significant ultrasonic degradation is not possible at the applied frequency of 20 kHz.