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.