Ionic liquids are gaining substantial interest as alternative reaction media. Despite the overwhelming amount of evidence suggesting a relationship between their structure and melting point, there still remains the problem of selectively choosing a particular ionic pair that will produce a liquid at room temperature. Ionic liquids based on 1-alkyl-3-methylimidazolium halides have been investigated using ab initio calculations utilizing Gaussian 98 and the 6-31G* and 6-31+G* basis sets. The calculated interaction energy was found to increase in magnitude with decreasing alkyl chain length at the Hartree-Fock level, although no trend was found to exist with increasing anionic radius. Correlations between melting point and interaction energy were investigated. Linear trends were found to exist in the 1-n-butyl-3-methylimidazolium (Bmim) halide series as well as the 1-alkyl-3-methylimidazolium iodide series.