The paper describes the basic physical regularities of material removal in Electrical discharge machining (EDM) of tool steel. One of the parameters, that material removal regularities quite accurately identifies, is the tool wear rate (TWR). This parameter, however, describes only the regularities concerning the tool electrode wear. More complex parameter for assessing regularities of material removal in EDM is thus electrode wear ratio (EWR). This parameter, except the size of the wear of the tool electrode, also describes the size of the workpiece material removal. Research on material removal was carried out on samples made out of tool steel EN X32CrMoV12-28 using Cu-ETP electrode EN CW004A. Aim of this paper was also based on the selection of main process parameters that significantly influence the material removal in EDM to define the individual specifics with regard to minimizing EWR.