Thermal properties of alkali bis(fluorosulfonyl)amides, Mf(2)N (M = Li, Na, K, Rb, Cs), have been examined as well as their binary mixtures. The eutectic compositions were determined by Tammann's rule, and the phase diagrams have been constructed for all of the binary systems. It has been revealed that the binary mixtures have melting points in the temperature range of (325 to 360) K which are much lower than that found for the corresponding perfluoroalkylsulfonylamide salts such as alkali bis(trifluoromethylsulfonyl)-amides, MTf(2)N, and alkali bis(pentafluoroethylsulfonyl)amides, MPf(2)N. The thermal properties of the single salts and binary mixtures are discussed for Mf(2)N, MTf(2)N, and MPf(2)N.