Focused ion beam (FIB) technique applications to very large scale integration (VLSI) failure analysis are reviewed. Three examples of microscopic cross sectioning andinsituobservation on a VLSI chip are presented. One is a cross section of an electromigration‐induced open circuit. Another shows a pinhole in the SiO2layer between the metal layer and the substrate. The third shows an open circuit, caused by process anomalies. Five preparation methods for further failure analysis are presented: cutting and connecting metal lines, making holes at insulation layer for electron beam probing, probing pad formation for mechanical and electron beam probing, microscopic cross sectioning for secondary electron miscroscopy observation, and marking for transmission electron spectroscopy observation. FIB was shown to be useful, as an aluminum microstructure observation tool, not only for qualitative observation of aluminum grains, but also for quantitative measurement of aluminum grain orientation. Each example is shown in many photographs.