The subjective nature of pain leads to many treatment difficulties. These problems can often be resolved if we know that the patient is trustworthy. Trustworthiness should be assessed as a distinct clinical variable. This is more easily achieved if we examine the three components of trustworthiness: the patient's subjective reports, which we call testimony; the reason that the patient seeks treatment, which we call motive; and the patient's adherence with efforts to get well, which we call responsibility. Because of difficulties with assessing testimony and motive, we propose that establishing the patient's responsibility is the key to assessing trustworthiness.