The phase diagram of the system InCl3/1-methyl-3-butylimidazolium chloride (MBIC) was constructed by DSC method. A clear colorless and transparent ionic liquid was experimentally observed in InCl3/MBIC system with about mole fraction of InCl3 X = 0.50 at ambient temperature. Both Raman scattering and ab initio calculations indicate that InCl4- is the predominant indium-containing species in this liquid. (C) 2003 Elsevier B.V. All rights reserved.