We have investigated the crystallization behavior of Pd 40 Ni 40 P 20 and Pd 42.5 Ni 7.5 Cu 30 P 20 bulk metallic glasses under ultrasonic (US) vibrations of MHz frequencies. Both metallic glasses were isothermally annealed at various temperatures under US vibrations, and the duration till the crystallization is completed (crystallization time) under US vibrations is compared with that without US vibrations. In both cases, the crystallization time for the US annealing was found to be much shorter than that without US vibrations. The X-ray diffraction profiles reveal that the crystalline phases obtained after the US annealing are identical to those obtained by the ordinary annealing without vibrations.