Recent research in the field of chronic pain has highlighted the importance of the assessment of psychological factors as part of the overall assessment of the chronic pain patient. Reliance only on self report of pain is inadequate. A number of different approaches have been taken to psychological evaluation, ranging from formal assessment of psychiatric illness to self-report questionnaires and clinical evaluation. In this chapter, each of the major types of assessment is described and illustrated with examples of specific tests or assessment instruments. The chapter highlights research which has attempted to appraise the relative value of different sorts of psychological information in assessment of the impact of pain or in the patient's response to treatment. Recommendations for the design of a simple comprehensive system for chronic pain are made.