This paper presents an experimental investigation of high speed milling of dies and molds. Several critical issues involved with the high speed milling of H13 tool steel of hardness up to 55 HR_C, have been studied and explained from a detailed analysis of experimental observations. The experiments were performed using several grades of PCBN ball-nose end mills with various edge preparations. The effect of different process parameters on the tool performance and the surface finish produced was also investigated. The cutting parameters involved were; cutting speeds in the range of 220 to 1320 m/min, feed variation from 0.0254 to 0.1 mm/tooth, axial depth of cut from 0.625 up to 2 mm, and radial width of cut of 0.254 mm. During the preliminary experimental investigation, the tilt angle was kept constant at 10 degrees. Several tests were conducted to study the effect of the different tool path directions on the cutting tool performance. Dry and wet cutting conditions were used and the effect of coolant on the tool life was also determined. The optimum cutting conditions have been specified based on the modes of tool failure, tool life and surface integrity produced.