HIP-produced high performance ceramics often need secondary machining. The investigation is concentrated on laser drilling of HIP-Si sub 3 N sub 4 and sialon using the single pulse technique. Experimental data give linear graphs for the specific energy vs. the pulse time and the power density vs. the inverse pulse time. The relationships are used for the construction of EP-diagrams, e.g. the relationship between specific energy and power density of the laser beam. From the EP-diagram can be found the energy consumption divided into different sources and different areas of machinability due to the power density