Clinical behavior analysis often targets the shaping of clients' functional interpretations of/or rules about his own behavior. These are referred to as clinically relevant behavior 3 (CRB3) in functional analytic psychotherapy (FAP). We suggest that CRB3s should be seen as contingency-specifying stimuli (CSS), due to the their ability to change the function of stimuli--including descriptions of variables involved in the client's behavioral problems as well as descriptions of variables associated with improvement or therapeutic change. This paper discusses the role of rule-governed behavior in FAP and the processes of shaping client interpretations of his or her behavior, and proposes that this may be an overlooked and important mechanism of change in FAP. To shape CRB3 in FAP, the therapist describes CSSs related to the therapy relationship that are consistent with the client's social environment, and reinforces improvements of the client's following his or her own newly shaped CSS descriptions during the session.