Book excerpt: Remarkable progress has been made in understanding both the psychological factors that influence pain, including attention, emotions and expectation, and psychological methods of pain control, such as hypnosis. This progress has several sources, including improved designs of both experimental and clinical studies and the interface of brain imaging with thoughtful questions. We have learned that pain can be powerfully influenced by addressing factors that pertain to the patients' perception of treatments. This book explains fundamental principles underlying the psychological control of pain. Understanding these principles fulfills an important need for those seeking a scientific understanding of pain control, as well as for those who treat pain patients.