The paper deals with the experimental study of the effect of an applied electrostatic field on ultrasonic machining of glass. Cylindrical cavities are machined in glass specimens (˜ 1-3 mm thick), both without and in the presence of a field. It is found that the time required for a 0-38 mm deep cut is reduced by about 10-20% due to the presence of a field. Further, the tool penetration rate is found to increase with the penetration of the tool into the workpiece. Using the analysis of variance technique, the observed data are analysed to show that the change in the rate of machining in the two cases is not due to chance but due to the presence of the field.