Anti-wear applications of ion-plated thin films have been investigated. Ion-plated films always showed better wear-resistance to fretting than the other vacuum-deposited films. Ion-plated chromium, gold, cadmium, zirconium, and boron carbide films have been effective in the prevention of fretting. Durability-surface was expressed three-dimensionally, and high hardness and large ion-radius were analyzed to be important factors for wear-resistance in air. Adhesion of coatings is critical to wear-resistance. Structures of film, interface, and substrate were studied with transmission and scanning electron microscopes and these all were found to be correlated with a good adhesion of ion-plated films. Microfibrous structure of film, microscopically intricate interface, and lattice defect concentration in substrate caused high adhesive strength of ion-plated films.