In recent years, it was reported that the new type of precipitation was found in nitrided iron alloys and called the cycle precipitation. When they were aged at 623 K, the growth and decomposition of Fe4N was cycled in quench aged ferrite matrix of nitrided iron alloys. Mean lengths of Fe4N precipitate were measured by the image analyzer. They showed 3-4 cycles of the growth and decomposition of Fe4N nitride in ferrite matrix up to 1000Ks aging at 623K. This precipitation behavior was shown by the large volume change. When pure iron transformed to Fe4N nitrid e, the volume increases remarkably and the expansion ratio is +16%. The average values of mean length of Fe4N decreased from 20 mum in nitrided Fe to 2-3 mum in Fe-Co and Fe-Ni alloys. In this paper, the precipitation behavior of Fe16N2 was studied in nitrided Fe-Co, Fe-Ni and other alloys. This Fe16N2 nitride is meta-stable phase in ferrite matrix and precipitates at low temperature aging. This nitride has volume expansion same as Fe4N nitride and the expansion ratio has +9%. Wire specimens of these alloys were used and were nitrided in at 923K in ammonia gas flow. After nitriding, they were tried quench aging and isothermal treatment at 433 to 498K in the silicon oil bath. And the same cycle precipitation was found in the precipitation process of Fe16N2 in these alloys.