The large fire ant decapitating fly, Pseudacteon litoralis Borgmeier, from northeastern Argentina was successfully released as a self-sustaining biocontrol agent of imported fire ants in south central Alabama in 2005. Five years later, this fly is firmly established at the original release site and has expanded outward at least 18 km. Nevertheless, populations remain very low considering P. litoralis is one of the most abundant fire ant decapitating flies in large areas of its range in South America. The reasons for low densities and why we were only able to establish this fly at 1 of 9 release sites in 4 states (2003–2006) are unknown, but problems with host-matching, release procedures, weather conditions, and competition with previously released decapitating flies are discussed as possible factors.