Li3InBr6-xClx was synthesized and the substitution effect on conductivity was investigated. Li3InBr6-xClx was single phase at all compositions. The volume of crystal lattice was decreased with Cl content and the rate of the decrease changed at x = 3. The conductivity of Li3InBr6-xClx had a maximum in Li3InBr3Clx and its value was 1.2 x 10(-4) Scm(-1) at 300 K. The activation energy of the conduction was at the minimum around x = 3 and its value was 20 kJ mol(-1). Phase transition temperature was lowered to be 285 K and the high conduction phase was stabilized by substitution Br with Cl. Li-7 NMR spectra in Li3InBr3Cl3 was sharp and it was confirmed that the diffusion of Li ion was fast at room temperature. (C) 2008 Elsevier B.V. All rights reserved.