Polycrystalline cubic boron nitride (pcBN) materials, which are produced by sintering cBN powder and binder material under ultra-high pressure and temperature conditions, have so high hardness, high thermal conductivity and very weak affinity for ferrous metals that pcBN has been used for cutting ferrous metals such as hardened steel, cast iron, powder metal heat resisting alloy or roll. In order to improve machining efficiency or accuracy, hard turning by pcBN material has been introduced instead of grinding process. High-speed cutting cast iron with pcBN material is one of the most important applications to reduce the production cost. pcBN also shows more excellent cutting performance than other tool materials for powder metal, heat resisting alloy and roll. This paper discribes the characteristics and the application examples of pcBN materials.