Strategies for validating complaints about pain and pain-related disability are considered important in the assessment of persons with chronic pain. Validation strategies should be based on principles of psychological assessment. In order to limit the amount of validating activities in clinical practice core outcome domains for subjects with chronic pain are identified (pain and bodily complaints, coping and treatment, level of physical, psychosocial, and cognitive functioning, working ability). Based on results from research on malingering the recommended validation strategies are multiple intra-individual comparisons of different levels and sources of data, use of reliable and valid tests and questionnaires, consideration of incidental inconsistencies, use of validating scales for response sets of acquiescence, social desirability, or defensiveness and symptom validity testing based on the principle of low item difficulties. The principles of validation are demonstrated exemplarily with respect to the selected outcome domains.