Part I: The Distinctive Theoretical Features of ACT. ACT, Human Suffering and Experiential Avoidance. Developments Within CBT: ACT and the Third Wave of Behaviour Therapy. Functional Contextualism. Relational Frame Theory. Acceptance. Cognitive Defusion. Self as Context. Contact with the Present Moment. Commitment. Values. Mindfulness and Behaviour Change: Toward Psychological Flexibility. ACT and CBT: Assumptive Differences. ACT and CBT: Strategic & Technical Differences. Empirical Matters. Part II: The Distinctive Practical Features of ACT. Overview of ACT’s Therapeutic Strategies. ACT-Based Case Conceptualization. Examining the Workability of the Control/Avoidance Agenda. Creative Hopelessness. Control is the Problem, Not the Solution. Introducing Willingness as the Alternative to Control. Promoting Active Acceptance. Cognitive Defusion I: Altering Language Conventions. Cognitive Defusion II: Objectifying Psychological Content. Cultivating Mindfulness to Promote Contact with the Present Moment. Contacting the Self-as-context. Clarifying Values. Values-based Goal and Action Planning. Building Larger Patterns of Committed Action. ACT in Groups and Non-clinical Contexts. ACT’s Therapeutic Stance.