Ultrathin　NiTi　miniature　strips　of　40-83　nm　in　thickness　were　fabricated　by　means　of　focused　ion　beam　milling　from　a　polycrystalline　NiTi　shape　memory　alloy.　The　NiTi　strips　were　subjected　to　tensile　deformation　inside　a　transmission　electron　microscope　using　a　self-designed　tension　apparatus　for　in　situ　examination　of　the　effect　of　thickness　on　the　stress　induced　martensitic　transformation　behavior　in　the　strips.　The　study　revealed　that　the　transformation　was　completely　suppressed　in　a　strip　of　40　nm　in　thickness　whereas　it　was　possible　in　thicker　strips.　In　these　strips,　the　stress　induced　martensitic　transformation　was　found　to　commence　sequentially　in　thicker　strips　first　and　then　in　thinner　strips　at　higher　strain　(stress)　levels,　demonstrating　the　size　effect.　This　size　effect　is　attributed　to　the　effect　of　damaged　surfaces,　including　a　Ga+-impregnated　amorphous　layer　on　one　side　of　the　strip　caused　by　sample　fabrication　using　FIB　and　oxidation　affected　layers　on　both　sides.　This　means　that　the　observed　＂size　effect＇＇　is　not　an　intrinsic　behavior　of　the　martensitic　transformation　in　NiTi　but　of　extrinsic　influences.　(C)　2013　Elsevier　B.V.　All　rights　reserved.