Thirty years ago, the first experimental demonstration was published showing that educators could improve significant challenging behavior in children with disabilities by replacing these behaviors with forms of communication that served the same purpose, a procedure called functional communication training (FCT). Since the publication of that paper, hundreds of demonstrations of the effectiveness of this approach have been published. This article describes the original study, the basic steps involved in using FCT, and how this approach can be used to reduce challenging behavior among toddlers and preschoolers.