This paper reviewed the recent progress in the environmental embrittlement of suicide. On the surface of suicides, the Si in the suicides such as Fe3(Si,Al) alloy reacts with both oxygen and water vapor more easy than with iron. A molecular hydrogen machanism of surface reaction, i. e. Si + 2H2O = SiO2 + 2H2, can be derived. The moisture-induced embrittlement of suicides can be considered to be an embrittlement in a localized high pressure molecular hydrogen condition. It is a kinetic hydrogen gas embrittlement. Suicides may have more severely intrinsic brittleness than iron aluminides due to their special electronic structure and bonding mechanism, leading to elucidate the role of environment on ductility with difficulty. The improvement of both the intrinsic brittleness and moisture-induced embrittlement are critical for the development of suicides.