Raman spectroscopic data are presented for the room-temperature molten salts (AlCl3)(x)(1-ethyl-3-methylimidazolium chloride)(1-x), for x ranging from 0.46 to 0.67. Ab initio molecular orbital theory has been used to compute the structure and vibrational frequencies of some of the anionic and cationic species present in these melts; the results are compared with semiempirical calculations and used to interpret the experiments.