Abstract Some gears may need to be hardened only at the surface without altering the chemical composition of the surface layers. Induction hardening may be a suitable processing choice in these cases. This chapter provides information on the wide variety of materials that can be induction hardened and on process details involved in induction hardening gears. It discusses the processes involved in heating, quenching, and tempering of gears. Information on surface hardness and case depth after induction hardening, induction hardening problems, the applications of induction hardening gears, and the advancements in induction hardening are also provided.