Within psychotherapy research traditions there are two cultures. One group of investigators, emphasizing the commonalities inherent in different schools of therapy and recognizing the extreme variability across clients and therapists, focuses on the interpersonal and emotional interactions between client and therapist as the agency of change in client well-being The other, characterized by the cognitive-behavioral approach and supporting the empirically-supported treatment movement, focuses on the replicable procedures and techniques designed for and tailored to symptom change within specific syndromes. Both approaches are now drawing together by virtue of the growing recognition that all therapy can be represented as the arrangement of social and psychological experiences that facilitate change. We discuss some implications of this change model and describe some of the complexities of the changes that take place within the course of psychotherapy. Some broad principles of change are suggested and related concepts, such as means-ends relationships, response interrelationships, and practical and psychological barriers to change are briefly outlined. The value of monitoring change in clients, a long-standing tradition in behavior therapy, is argued, with one additional twist proposed, namely the monitoring of client experiences and actions that themselves facilitate change, regardless of the targeted problem area.

Key words: principles of change, trajectories, means-ends relationships, context, contingencies