High speed machining has received important interest because it leads to an increase in productivity and a better workpiece surface quality. Experimental investigation of the impact of tool materials and cutting parameters on surface roughness in high speed machining is presented in this paper. The surface roughness of machined workpiece is measured when high speed face milling of hardened carbon steels and cast iron by using PCBN and ceramic tools at various combinations of cutting speed and feed rate. The experimental results show that the surface roughness tends to decrease with increases of the cutting speed, but further increases of cutting speed cause an increase in surface roughness. Lower surface roughness is obtained by using less feed rate at high cutting speed region, which is as expected the same as at conventional cutting speeds. It is anticipated that the minimum surface roughness could be obtained by selecting the appropriate cutting speed and feed rate for the given material pairs between workpiece and cutting tool.