Amorphous solid electrolytes in the system Li2S-P2S5 were prepared from a mixture of crystalline Li2S and P2S5 using a mechanical milling technique at room temperature. In the composition range x less than or equal to 87.5 of xLi(2)S(.)(100-X)P2S5, conductivities of the glassy powders mechanically milled for 20 h were as high as 10(-4) S cm(-1) at room temperature. The heat treatment of the 80Li(2)S(.)20P(2)S(5) glassy powders at around 220 degreesC produced dense glass-ceramics with high conductivity around 10(-3) S cm(-1) at room temperature. The crystallization of conductive phases of Li7PS6, Li3PS4 and unknown crystals from the glass matrix and the decrease of grain boundaries by the softening of the glassy powders are simultaneously achieved at relatively low temperatures, around 220 degreesC.