µEDM (micro-electrical discharge machining) is a process for machining conductive materials without mechanical contact; it is particularly suitable for machining hard materials. The principle consists in creating electrical discharges between a micro-tool and a workpiece, both of which are immersed in a dielectric. It is a complementary process to mechanical, laser, micro-machining techniques, and even to techniques derived from silicon microtechnology (RIE, DRIE, LIGA). However, the resolution of µEDM is limited; it depends on several electrical and physical parameters. The goal of this paper is to characterize the holes obtained by drilling using µEDM with different micro-tool diameters (Φ = 250 µm; Φ = 80 µm; Φ = 40 µm; Φ = 20 µm) for an experimental time of t = 2 h. The results obtained let us conclude that a large diameter micro-tool (Φ = 250 µm) leads to removing a larger amount of material (43×10  µm  ) than small diameters: Φ = 80 µm; Φ = 40 µm; Φ = 20 µm where the removed volume is equal to 2.6×10  µm  ; 10  µm  ; 0.4 × 10  µm  , respectively. The electrode-tool diameter influences the maximum depth of the holes; a diameter of Φ = 250 µm generates a hole where the maximum depth is 170 µm while small diameters: Φ = 80 µm; Φ = 40 µm; Φ = 20 µm provide holes with a depth of 82 µm; 51 µm; 50 µm respectively. Through these experiments, we can also conclude that the lateral gap of the holes is almost constant. It is about 40 µm whatever the diameter.