Relational Frame Theory (RFT) has made a very respectable empirical and theoretical showing in the psychological literature during the past decade, but the theory still remains unknown or unappreciated by most cognitive and behavioral psychologists. This article highlights why this might be the case, and presents RFT in a simplified, systematic manner, in part by comparing it to a well-known cognitive model. Finally, the article outlines RFT's relatively unique contributions to psychological accounts of language and cognition, and addresses some of RFT's scientific and applied implications. ********** Relational Frame Theory (RFT) has had a notable presence in the psychology literature since its development over a decade ago. Well over 30 empirical RFT studies have been published in peer-reviewed psychology journals in the past 10 years, and an even larger number of theoretical and descriptive treatments of it have been published as well. Recently, a book length treatment of RFT has been made available (Hayes, Barnes-Holmes, & Roche, 2001), summarizing supporting data and extending RFT analyses to a variety of psychological phenomena. In addition, RFT principles form the theoretical background of Acceptance and Commitment Therapy (ACT; see, for example, Hayes, Strosahl, & Wilson, 1999). Given the relatively frequent appearances of Relational Frame Theory in psychological literature, it is perhaps surprising that the theory remains virtually unknown outside behavioral circles, and even unrecognized or misunderstood by many academic behavioral psychologists. RFT has largely escaped notice and comprehension for at least three reasons. First, RFT intentionally makes use of technical, non-colloquial language to allow a scientific treatment of cognition. As such, published descriptions of RFT are undeniably technical, and not readily accessible to those who have not spent a considerable amount of time trying to understand the theory. Second, its significance and relevance to human psychopathology and language in general do not immediately seem obvious due to its nontraditional account of these phenomena. Finally, non-behavioral psychologists have long assumed that behaviorism has little or nothing to offer to the understanding of human language and cognition. Theories of these fundamentally important human processes that arise from the behavioral tradition are thus easy to ignore. The first purpose of this article is to convey the principles of Relational Frame Theory in relatively easy to understand fashion. In doing so, it is hoped that what RFT has to do with language, cognition, and psychopathology will become apparent. Since a vast amount of cognitive literature regarding these topic areas currently exists, RFT's relatively unique and important contributions to this literature will be outlined as well. To accomplish these goals, a popular and widely-known cognitive model of a "fear network" (Lang, 1985) will first be presented and briefly described. Lang's model contains some cosmetic similarities to RFT that will hopefully orient the reader to the analysis that follows. Following the description of this model, an RFT account of the same information presented in the model will be advanced, allowing a systematic introduction to the reader of the defining features of RFT. Finally, several reasons why RFT offers a unique and important approach to language, cognition, and human suffering will be described. Empirical evidence and more extensive arguments of technical points about RFT made throughout the article can be found, for example, in Hayes et al. (2001). RELATIONAL FRAME THEORY: BASICS AND APPLICATIONS Lang's Fear Network Lang's (1985) exemplary model of a fear network is presented succinctly in Figure 1. Stimulus propositions (indicated in ovals in Figure 1) involve "information about prompting external stimuli and the context in which they occur," and response propositions refer to "information about responding in this context, including expressive verbal behavior, overt acts, and the visceral and somatic events that mediate arousal and actions" (p. …