Ternary phase diagrams of alkali bis(trifluoromethylsulfonyl)amides, MTf(2)N (M = Li, Na, K, Cs), have been constructed, and their eutectic compositions and temperatures have been determined. For binary MTf2N systems, existences of intermediate compounds, Li(2)K(Tf(2)N)(3) and LiCs(Tf(2)N)(2), have been newly confirmed by X-ray diffraction, and eutectic temperatures have been revised by more precise differential scanning calorimetry.