This study examined the relationship of self-reports of illness behavior to pain ratings and overt pain behaviors in a group of chronic low back pain patients referred for pain management. Illness behavior was measured using the Pilowsky and Spence Illness Behavior Questionnaire (IBQ) and pain behavior was recorded using a standard behavioral observation method. Multivariate regression analyses revealed that scores on the IBQ were highly predictive of a variety of indices of pain and pain behavior. These results were obtained even after controlling for significant demographic and medical status variables. The findings of this study support the utility of the IBQ in the behavioral assessment of chronic pain patients. © 1986.