A GOOD ORTHODONTIC WIRE IS ONE THAT CAN EXERT A CONTINUING CONSTANT FORCE DURING CLINICAL TREATMENT OF THE TEETH. NI-TI (NITINOL) WIRES ARE DESIRABLE BECAUSE THEY CAN PRODUCE AN ALMOST CONSTANT FORCE TOGETHER WITH SUCH DESIRABLE PROPERTIES AS STRENGTH, STIFFNESS, FORMABILITY, WELD ABILITY AND CAPABILITY TO BE SOLDERED. IT IS THEREFORE APPROPRIATE TO INVESTIGATE THE NI-TI MECHANICAL AND METALLOGRAPHIC PROPERTIES IN ORDER TO UNDERSTAND THEIR ACTUAL BEHAVIOR UNDER CLINICAL TREATMENT AS COMPARED TO THOSE OF THE OTHER POPULAR ORTHODONTIC WIRES. IN THIS RESEARCH, WE HAVE FIRST DETERMINED THE LOADING–UNLOADING CURVES OF A NUMBER OF SUPER ELASTIC NI-TI WIRES BY THREE-BRACKET BENDING METHOD AND THEN COMPARED THEIR BEHAVIOR TO INTRODUCE THE MOST SUITABLE ONE WITH RESPECT TO THE SPECIFIC CLINICAL APPLICATION. STRUCTURAL STUDIES REVEALED THAT THE LOW-TEMPERATURE APPLICATION OF STRESS DURING LOADING-UNLOADING TESTS DOES NOT AFFECT THE MORPHOLOGY OF THE SUPERELASTIC SPECIMENS, WHILE THIS SEEMED REVERSE IN THE SHAPE MEMORY NITI WIRES.