The correct selection of the machining parameters is one of the most significant issues to take into consideration in Ultrasonic-assisted Electrical Discharge Machining (US-EDM) and EDM processes. In the present work, a study has been made to develop and extract statistical models to show the relationship between important machining performance data (material removal rate (MRR), tool wear ratio (TWR) and surface roughness Ra) and the input machining parameters (pulse current, and pulse-on time) in the EDM and US-EDM of AISI H13. The models obtained were used to analyze the effects of input parameters on machining performance. In addition, a comparative study was carried out to investigate the effect of ultrasonic vibration of the workpiece on machining performance. The results show that Ultrasonic vibration of the workpiece can significantly reduce the inactive pulses and improves the stability of process. Also US-EDM is effective in attaining a high material removal rate (MRR) in finishing regime in comparison with conventional EDM. The results of Analysis of Variance (ANOVA) indicate that the proposed mathematical models can adequately explain the performance within the limits of the factors being studied.