Amorphous solid electrolytes containing large amount of Li2S were prepared in the system Li2S-GeS2-P2S5 by a high-energy ball-milling process. The region of amorphous-sample formation by the ball-milling process is much wider than the glass-forming region by a conventional melt-quenching method. The addition of a second network-forming sulfide, GeS2, to the Li-2-P2S5 system caused ail enhancement of ion conductivities of the amorphous samples. The 95Li(3)PS(4)(.)5Li(4)GeS(4) amorphous sample showed the highest lithium-ion conductivity 4.0 x 10(-4) S cm(-1) at room temperature among the obtained amorphous samples in the system Li2S-GeS2-P2S5. DC polarization measurements suggested that lithium-ion transport number of the 95Li(3)PS(4)(.)5Li(4)GeS(4) sample was almost unity. (C) 2004 Elsevier B.V. All rights reserved.