- Action theory (AT) is an emerging theoretical and empirical paradigm that is based on multiple perspectives. The common denominator of these perspectives is their depiction of the individual as actively shaping his or her interpersonal environment. The purpose of this special section is to evaluate the impact of AT on clinical psychology. To that effect, articles that focus on a broad range of topics, including stress and depression, chronic pain, child and adolescent development, clinical case formulation, psychotherapy for suicidal patients, and public mental health policy in relation to recovery from psychosis have been assembled. Presenting novel conceptualizations and data on the ways in which individuals actively shape their environment, these articles highlight the potential of AT for improving clinical science and practice. © 2006 Wiley Periodicals, Inc. J Clin Psychol 62: 1053–1064, 2006.