Functional Analytic Psychotherapy (FAP) targets a client's interpersonal behavior for change with the goal of improving his or her quality of life. One question guiding FAP case conceptualization is, "What interpersonal behavioral repertoires will allow a specific client to function optimally?" Previous FAP writings have suggested that a therapist must consider two issues when answering this question: (1) the client's values and (2) the interpersonal behaviors that will be supported by the client's social community. This paper discusses the potential for a single "universal" case conceptualization that can be successfully used with all FAP clients. A number of possible universal conceptualizations are reviewed but ultimately rejected as legitimate candidates. As an alternative, the authors suggest the use of a foundational framework for FAP case conceptualization focused on developing goal-directed interpersonal flexibility in clients. This framework has the benefits of: (1) identifying target repertoires that may be necessary but are not sufficient for the successful interpersonal functioning of all clients, (2) allowing for a functional, principle-based conceptualization of a client's specific target behaviors, and (3) encouraging consideration of a client's unique values and social community. (Contains 12 footnotes.)