Since the original publication of this seminal work, acceptance and commitment therapy (ACT) has come into its own as a widely practiced approach to helping people change. This book provides the definitive statement of ACT--from conceptual and empirical foundations to clinical techniques--written by its originators. ACT is based on the idea that psychological rigidity is a root cause of a wide range of clinical problems. The authors describe effective, innovative ways to cultivate psychological flexibility by detecting and targeting six key processes: defusion, acceptance, attention to the present moment, self-awareness, values, and committed action. Sample therapeutic exercises and patient-therapist dialogues are integrated throughout. New to This Edition*Reflects tremendous advances in ACT clinical applications, theory building, and research. *Psychological flexibility is now the central organizing focus. *Expanded coverage of mindfulness, the therapeutic relationship, relational learning, and case formulation.*Restructured to be more clinician friendly and accessible; focuses on the moment-by-moment process of therapy.