This paper comprehensively evaluates the influence of ultrasonic irradiation of spark gap on EDM characteristics for both planing and drilling operations. A set of comparative experiments were carried out and the analysis of the results was based on standard statistical techniques. The response surfaces and the corresponding response functions were determined for major performance indices, such as machining rate, tool wear rate, corresponding wear ratio and surface roughness. With the application of ultrasonics the machining rate and surface finish improved significantly and, although the tool wear rate also increased, the wear ratio was not influenced significantly. The improvement in machining rate was highly significant in the drilling operation.