The apparatus and technique for preparing thin sections of nonmetals suitable for transmission electron microscopy are described. The last stage of the thinning process involves bombardment with argon ions. The optimum operating conditions of the discharge tube were established for near stoichiometric rutile (TiO2), and the quality of the sections evaluated by observation at 100 kV in an electron microscope. Specimens having (001), (110), and (100) surfaces were successfully prepared, and no damage was in evidence as a result of the nature of the preparation. It is believed the technique can be extended to the preparation of thin sections suitable for transmission electron microscopy of metals, as well as other nonmetals.