Human macrophage colony stimulating factor(hM-CSF) inclusion bodies expressed in E.coli were dissociated successfully by high intensity ultrasound in a suspension of 4mol/L urea instead of using 8 mol/L urea as solvent.The SDS-PAGE of suspension samples processed by ultrasound shows the same band at 17 000 as that solubilized by 8 mol/L urea.The results show the possibility of developing a new ultrasonic technique for the dissociation of inclusion bodies.