Problem behaviors such as aggression, self-injury, and tantrums can serve as major obstacles to even the most sophisticated intervention programs. Fortunately, there have been recent advances in our understanding of the nature of these behaviors, and as a result, new treatments for these behaviors have been developed. This article describes one such innovation—functional communication training, which involves teaching alternative communication to replace problem behavior. A great deal of research exists on the efficacy of this approach. This article reviews the literature outlining the conditions under which this intervention is successful and provides a comparison with other behavioral approaches to intervention. Functional communication training is an empirically validated approach to positive behavioral support for challenging behavior.