In this study, the effects of cryogenic treatment (CT) on the performance of CuCrZr alloy and Cu electrodes in electro discharge machining (EDM) of AISI P20 tool steel were investigated experimentally. For this purpose, a group of electrodes were cryogenically treated at 140 degrees C for 30 min and then tempered at 175 degrees C for 1 h. The tool performance was evaluated in terms of electrode wear rate (EWR), material removal rate (MRR), and average surface roughness (Ra) of machined surfaces. The EDM tests were conducted at pulse currents of 4, 8, 12, and 16 A and pulse durations of 25 and 50 is. Experimental results showed that treated electrodes were less worn than the untreated ones and the Ra values of machined surfaces decreased when cryo-treated electrodes were used. Also, it was observed that pulse current is the most effective parameter in the EDM process.