Acceptance and Commitment Therapy examines the therapy's history and process, evaluates the therapy's evidence base and effectiveness, and suggests future directions in the therapy's development. Acceptance and Commitment Therapy (ACT) is a unique empirically based psychological intervention that uses acceptance and mindfulness processes, and commitment and behavior change processes to produce psychological flexibility. Steven C. Hayes, who helped develop ACT, and co-author Jason Lillis provide an overview of ACT's main influences and its basic principles. In this succinct and understandable survey, the authors show how ACT illuminates the ways that language encourages unhelpful skirmishing in clients' psychic lives, and how to use ACT to help clients accept private experiences, become more mindful of thoughts, develop greater clarity about personal values, and commit to needed behavior change.