Objective. To investigate the relationship between cortisol levels, pain intensity, and negative mood in chronic pain patients participating in a multidisciplinary pain management program.Patients. Eighteen chronic pain patients collected saliva samples over several days both directly before and after attending a 4-week multidisciplinary pain management program.Outcome Measures. Saliva samples were assayed for their cortisol concentration. Participants also completed self-report measures of pain intensity and depression.Results. Usual pain intensity and waking cortisol levels changed in parallel following treatment, as did changes in depression and cortisol levels late in the morning and in the evening. Depression did not mediate the association between cortisol and usual pain intensity; neither did pain intensity moderate the association between cortisol and depression.Conclusions. Changes in cortisol secretion may provide a useful biological marker of treatment outcome in chronic pain patients after their participation in a multidisciplinary pain management program.