Functional Analytic Psychotherapy (FAP), a therapy based on radical behaviorism, establishes the priority of the therapeutic interaction as a mechanism of change in psychotherapy. Since the first book on FAP appeared in 1991, it has been the focus of many papers and has been incorporated by the community of behavior therapists. This paper is a review of 80 international publications on FAP from 1990 to 2010, including publications from Brazil, the United States, Spain, Switzerland and Colombia. The goal was to analyze how FAP has been treated and developed across these 20 years, and also to propose some directions for further studies. The analysis suggests a diverse range of FAP publications, points to the necessity of more empirical studies with tighter control of variables and objective measurement of data to better understand FAP's process and effectiveness, and highlights the importance of increased communication between international research groups to increase the potential benefits of singular and collective research efforts on FAP. (Contains 2 tables and 7 figures.)