Technical Abstract: We describe the odorant binding proteins (OBPs) of the red imported fire ant, Solenopsis invicta, obtained from analyses of a single EST library and data generated from separate 454 sequencing runs of two normalized cDNA libraries. We identified a total of 18 OBPs in this ant, which is the smallest OBP repertoire found in an insect to date. A third of the fire ant OBPs are orthologs to honey bee OBPs. Another third of the OBPs belong to a lineage-specific expansion, which is a common feature of insect OBP evolution. Like other OBPs, the different fire ant OBPs share little sequence similarity (~20%), which makes evolutionary analyses difficult. Tests of sequence saturation indicate there is little phylogenetic signal in the sequences, which is consistent with the large variation in alignment lengths from different multiple sequence alignment methods. However, the phylogenies derived from all alignments consistently capture similar topological features, suggesting some evolutionary information is retained in the sequences. Analyses for positive selection were highly sensitive to alignment method, precluding any reliable inferences. As previously suggested, our results underscore the importance for careful exploration of the sensitivity to the effects of alignment methods for data comprising widely divergent sequences.