Argon ion sputter etching was applied to a Ti 15V 3Cr 3Al 3Sn alloy 15 3 alloy specimen placed on a SUS304 stainless steel cathode disk and commercially pure titanium pure Ti specimens placed on a vanadium V , tantalum Ta , niobium Nb , molybdenum Mo , tungsten W disk, respectively. The sputter etching of the 15 3 alloy on the SUS304 disk and pure Ti specimen on the V or Ta disks formed ne dense holes with diameters smaller than 500 nm at a sputter power of 250 W for 0.9 3.6 ks. On the other hand, the sputter etching of the pure Ti specimen on the Nb, Mo, or W disks formed ne column or ridge shaped protrusions with sizes smaller than 1 µm. Because EDX analyses showed a certain amount of V, Ta, Nb, Mo, or W on the pure Ti specimens, we consider that the formation of ne holes or protrusions were due to particles from each cathode disk dissolving into the Ti matrix to form two ne regions with different composition and sputter rate; i.e., the holes were formed by preferential sputtering of Ti atoms in the regions with small V or Ta composition. For the 15 3 alloy, the formation of ne holes seemed to be caused by the preferential sputtering of Ti atoms in the regions with smaller V.