Articles made of single crystal copper-aluminum-nickel superelastic alloys exhibit large shape recovery and would be useful in medical devices were it not for the perception that their large copper content must cause deleterious interaction with living tissue. However, results of MEM elution cell cytotoxicity, iso intramuscular implant, and hemo-compatibility tests performed at a commercial laboratory produced negative results. This can be interpreted as resulting from formation of a durable oxide surface layer analogous to the titanium oxide layer that inhibits body fluid reaction to titanium nickel alloys. Alternatively, the non-existence of crystal domain boundaries may itself inhibit corrosive chemical attack. Experimental biocompatibility results, surface analysis, and suggested applications are discussed.