Proper selection of materials and devices has a decisvie influence on the performance of an orthodontic appliance. Above all, forces and torques depend on the wire alloy and cross section. This lecture gives a survey of the basic material properties of superelastic NiTi alloys, their clinical force systems, and their intraoral corrosion behavior and biocompatibility. A further aspect of orthodontic material science of particular importance is the frictional behavior of bracket/wire combinations in arch guided tooth movement. Physical background, affecting material parameters, and results for various bracket/wire systems are discussed with a special emphasis on self ligating brackets.